diff --git a/packages/babel-helper-replace-supers/src/index.js b/packages/babel-helper-replace-supers/src/index.js
index da1437fa80..a034093a0d 100644
--- a/packages/babel-helper-replace-supers/src/index.js
+++ b/packages/babel-helper-replace-supers/src/index.js
@@ -106,6 +106,7 @@ export default class ReplaceSupers {
     this.isStatic = opts.isStatic;
     this.hasSuper = false;
     this.inClass = inClass;
+    this.inConstructor = opts.inConstructor;
     this.isLoose = opts.isLoose;
     this.scope = this.methodPath.scope;
     this.file = opts.file;
@@ -123,6 +124,7 @@ export default class ReplaceSupers {
   isStatic: boolean;
   hasSuper: boolean;
   inClass: boolean;
+  inConstructor: boolean;
   isLoose: boolean;
   scope: Scope;
   file;
@@ -132,6 +134,7 @@ export default class ReplaceSupers {
     methodPath: NodePath,
     methodNode: Object,
     superRef: Object,
+    inConstructor: boolean,
     isStatic: boolean,
     isLoose: boolean,
     file: any,
@@ -174,10 +177,18 @@ export default class ReplaceSupers {
    */
 
   getSuperProperty(property: Object, isComputed: boolean): Object {
+    let thisExpr = t.thisExpression();
+    if (this.inConstructor) {
+      thisExpr = t.callExpression(
+        this.file.addHelper("assertThisInitialized"),
+        [thisExpr],
+      );
+    }
+
     return t.callExpression(this.file.addHelper("get"), [
       getPrototypeOfExpression(this.getObjectRef(), this.isStatic),
       isComputed ? property : t.stringLiteral(property.name),
-      t.thisExpression(),
+      thisExpr,
     ]);
   }
 
diff --git a/packages/babel-helpers/src/helpers.js b/packages/babel-helpers/src/helpers.js
index 1349696a22..2ac4251c02 100644
--- a/packages/babel-helpers/src/helpers.js
+++ b/packages/babel-helpers/src/helpers.js
@@ -509,12 +509,24 @@ helpers.objectWithoutProperties = defineHelper(`
   }
 `);
 
+helpers.assertThisInitialized = defineHelper(`
+  export default function _assertThisInitialized(self) {
+    if (self === void 0) {
+      throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
+    }
+    return self;
+  }
+`);
+
 helpers.possibleConstructorReturn = defineHelper(`
   export default function _possibleConstructorReturn(self, call) {
     if (call && (typeof call === "object" || typeof call === "function")) {
       return call;
     }
-    if (!self) {
+    // TODO: Should just be
+    //   import assertThisInitialized from "assertThisInitialized";
+    //   return assertThisInitialized(self);
+    if (self === void 0) {
       throw new ReferenceError("this hasn't been initialised - super() hasn't been called");
     }
     return self;
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/derived/expected.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/derived/expected.js
index 6a729c8c02..5615c3cffb 100644
--- a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/derived/expected.js
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/derived/expected.js
@@ -7,7 +7,7 @@ function (_Bar) {
     var _temp, _this;
 
     babelHelpers.classCallCheck(this, Foo);
-    return babelHelpers.possibleConstructorReturn(_this, (_temp = _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this, ...args)), Object.defineProperty(_this, "bar", {
+    return babelHelpers.possibleConstructorReturn(_this, (_temp = _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this, ...args)), Object.defineProperty(babelHelpers.assertThisInitialized(_this), "bar", {
       configurable: true,
       enumerable: true,
       writable: true,
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/foobar/expected.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/foobar/expected.js
index 2865c35414..4c8e9df931 100644
--- a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/foobar/expected.js
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/foobar/expected.js
@@ -8,7 +8,7 @@ function (_Parent) {
 
     babelHelpers.classCallCheck(this, Child);
     _this = babelHelpers.possibleConstructorReturn(this, (Child.__proto__ || Object.getPrototypeOf(Child)).call(this));
-    Object.defineProperty(_this, "scopedFunctionWithThis", {
+    Object.defineProperty(babelHelpers.assertThisInitialized(_this), "scopedFunctionWithThis", {
       configurable: true,
       enumerable: true,
       writable: true,
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-call/expected.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-call/expected.js
index 4806970bce..edd181b05b 100644
--- a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-call/expected.js
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-call/expected.js
@@ -23,11 +23,11 @@ function (_A) {
     var _temp, _this;
 
     babelHelpers.classCallCheck(this, B);
-    return babelHelpers.possibleConstructorReturn(_this, (_temp = _this = babelHelpers.possibleConstructorReturn(this, (B.__proto__ || Object.getPrototypeOf(B)).call(this, ...args)), Object.defineProperty(_this, "foo", {
+    return babelHelpers.possibleConstructorReturn(_this, (_temp = _this = babelHelpers.possibleConstructorReturn(this, (B.__proto__ || Object.getPrototypeOf(B)).call(this, ...args)), Object.defineProperty(babelHelpers.assertThisInitialized(_this), "foo", {
       configurable: true,
       enumerable: true,
       writable: true,
-      value: babelHelpers.get(B.prototype.__proto__ || Object.getPrototypeOf(B.prototype), "foo", _this).call(_this)
+      value: babelHelpers.get(B.prototype.__proto__ || Object.getPrototypeOf(B.prototype), "foo", babelHelpers.assertThisInitialized(_this)).call(_this)
     }), _temp));
   }
 
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-expression/expected.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-expression/expected.js
index 1c370a24b3..aaa16b44ee 100644
--- a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-expression/expected.js
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-expression/expected.js
@@ -7,7 +7,7 @@ function (_Bar) {
     var _temp, _this;
 
     babelHelpers.classCallCheck(this, Foo);
-    foo((_temp = _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this)), Object.defineProperty(_this, "bar", {
+    foo((_temp = _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this)), Object.defineProperty(babelHelpers.assertThisInitialized(_this), "bar", {
       configurable: true,
       enumerable: true,
       writable: true,
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-statement/expected.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-statement/expected.js
index b741a00fe2..5c9c26143b 100644
--- a/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-statement/expected.js
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/general/super-statement/expected.js
@@ -8,7 +8,7 @@ function (_Bar) {
 
     babelHelpers.classCallCheck(this, Foo);
     _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
-    Object.defineProperty(_this, "bar", {
+    Object.defineProperty(babelHelpers.assertThisInitialized(_this), "bar", {
       configurable: true,
       enumerable: true,
       writable: true,
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/regression/6154/expected.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/regression/6154/expected.js
index c027b23cbc..c272ca164b 100644
--- a/packages/babel-plugin-proposal-class-properties/test/fixtures/regression/6154/expected.js
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/regression/6154/expected.js
@@ -2,7 +2,7 @@ function _typeof(obj) { if (typeof Symbol === "function" && typeof Symbol.iterat
 
 function _instanceof(left, right) { if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) { return right[Symbol.hasInstance](left); } else { return left instanceof right; } }
 
-function _possibleConstructorReturn(self, call) { if (call && (_typeof(call) === "object" || typeof call === "function")) { return call; } if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+function _possibleConstructorReturn(self, call) { if (call && (_typeof(call) === "object" || typeof call === "function")) { return call; } if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
 
 function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
 
@@ -10,6 +10,8 @@ function _classCallCheck(instance, Constructor) { if (!_instanceof(instance, Con
 
 function _get(object, property, receiver) { if (object === null) object = Function.prototype; var desc = Object.getOwnPropertyDescriptor(object, property); if (desc === undefined) { var parent = Object.getPrototypeOf(object); if (parent === null) { return undefined; } else { return _get(parent, property, receiver); } } else if ("value" in desc) { return desc.value; } else { var getter = desc.get; if (getter === undefined) { return undefined; } return getter.call(receiver); } }
 
+function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
 var Test = function Test() {
   var _this2 = this;
 
@@ -31,12 +33,12 @@ var Test = function Test() {
         args[_key] = arguments[_key];
       }
 
-      return _possibleConstructorReturn(_this, (_temp = _this = _possibleConstructorReturn(this, (_ref = Other.__proto__ || Object.getPrototypeOf(Other)).call.apply(_ref, [this].concat(args))), Object.defineProperty(_this, "a", {
+      return _possibleConstructorReturn(_this, (_temp = _this = _possibleConstructorReturn(this, (_ref = Other.__proto__ || Object.getPrototypeOf(Other)).call.apply(_ref, [this].concat(args))), Object.defineProperty(_assertThisInitialized(_this), "a", {
         configurable: true,
         enumerable: true,
         writable: true,
         value: function value() {
-          return _get(Other.prototype.__proto__ || Object.getPrototypeOf(Other.prototype), "test", _this);
+          return _get(Other.prototype.__proto__ || Object.getPrototypeOf(Other.prototype), "test", _assertThisInitialized(_this));
         }
       }), _temp));
     }
@@ -49,7 +51,7 @@ var Test = function Test() {
     enumerable: true,
     writable: true,
     value: function value() {
-      return _get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this2);
+      return _get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _assertThisInitialized(_this2));
     }
   });
 };
diff --git a/packages/babel-plugin-transform-classes/src/vanilla.js b/packages/babel-plugin-transform-classes/src/vanilla.js
index 027ee8d287..8064a37511 100644
--- a/packages/babel-plugin-transform-classes/src/vanilla.js
+++ b/packages/babel-plugin-transform-classes/src/vanilla.js
@@ -17,22 +17,6 @@ const noMethodVisitor = {
 const verifyConstructorVisitor = traverse.visitors.merge([
   noMethodVisitor,
   {
-    MemberExpression: {
-      exit(path) {
-        const objectPath = path.get("object");
-        if (this.isDerived && !this.hasBareSuper && objectPath.isSuper()) {
-          const hasArrowFunctionParent = path.findParent(p =>
-            p.isArrowFunctionExpression(),
-          );
-          if (!hasArrowFunctionParent) {
-            throw objectPath.buildCodeFrameError(
-              "'super.*' is not allowed before super()",
-            );
-          }
-        }
-      },
-    },
-
     CallExpression: {
       exit(path) {
         if (path.get("callee").isSuper()) {
@@ -48,14 +32,20 @@ const verifyConstructorVisitor = traverse.visitors.merge([
     },
 
     ThisExpression(path) {
-      if (this.isDerived && !this.hasBareSuper) {
-        const fn = path.find(p => p.isFunction());
-
-        if (!fn || !fn.isArrowFunctionExpression()) {
-          throw path.buildCodeFrameError(
-            "'this' is not allowed before super()",
-          );
+      if (this.isDerived) {
+        if (path.parentPath.isMemberExpression({ object: path.node })) {
+          // In cases like this.foo or this[foo], there is no need to add
+          // assertThisInitialized, since they already throw if this is
+          // undefined.
+          return;
         }
+
+        const assertion = t.callExpression(
+          this.file.addHelper("assertThisInitialized"),
+          [path.node],
+        );
+        path.replaceWith(assertion);
+        path.skip();
       }
     },
   },
@@ -271,6 +261,7 @@ export default class ClassTransformer {
             methodNode: node,
             objectRef: this.classRef,
             superRef: this.superName,
+            inConstructor: isConstructor,
             isStatic: node.static,
             isLoose: this.isLoose,
             scope: this.scope,
@@ -444,10 +435,6 @@ export default class ClassTransformer {
     const path = this.userConstructorPath;
     const body = path.get("body");
 
-    if (!this.hasBareSuper && !this.superReturns.length) {
-      throw path.buildCodeFrameError("missing super() call in constructor");
-    }
-
     path.traverse(findThisesVisitor, this);
 
     let guaranteedSuperBeforeFinish = !!this.bareSupers.length;
@@ -469,7 +456,11 @@ export default class ClassTransformer {
             return true;
           }
 
-          if (parentPath.isLoop() || parentPath.isConditional()) {
+          if (
+            parentPath.isLoop() ||
+            parentPath.isConditional() ||
+            parentPath.isArrowFunctionExpression()
+          ) {
             guaranteedSuperBeforeFinish = false;
             return true;
           }
@@ -485,9 +476,13 @@ export default class ClassTransformer {
 
     if (this.isLoose) {
       wrapReturn = returnArg => {
+        const thisExpr = t.callExpression(
+          this.file.addHelper("assertThisInitialized"),
+          [thisRef()],
+        );
         return returnArg
-          ? t.logicalExpression("||", returnArg, thisRef())
-          : thisRef();
+          ? t.logicalExpression("||", returnArg, thisExpr)
+          : thisExpr;
       };
     } else {
       wrapReturn = returnArg =>
@@ -500,7 +495,7 @@ export default class ClassTransformer {
     // if we have a return as the last node in the body then we've already caught that
     // return
     const bodyPaths = body.get("body");
-    if (bodyPaths.length && !bodyPaths.pop().isReturnStatement()) {
+    if (!bodyPaths.length || !bodyPaths.pop().isReturnStatement()) {
       body.pushContainer(
         "body",
         t.returnStatement(
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js
index 3c808277b6..a8e18067dd 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js
@@ -1,3 +1,5 @@
+function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
 function _inheritsLoose(subClass, superClass) { subClass.prototype = Object.create(superClass.prototype); subClass.prototype.constructor = subClass; subClass.__proto__ = superClass; }
 
 let B = function B() {};
@@ -11,7 +13,7 @@ function (_B) {
     var _this;
 
     if (track !== undefined) _this = _B.call(this, track) || this;else _this = _B.call(this) || this;
-    return _this;
+    return _assertThisInitialized(_this);
   }
 
   return A;
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/exec.js
new file mode 100644
index 0000000000..b4aedfd3f5
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/expected.js
new file mode 100644
index 0000000000..ecb4d54469
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/expected.js
@@ -0,0 +1,13 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inheritsLoose(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    return babelHelpers.assertThisInitialized(_this);
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/options.json b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/options.json
deleted file mode 100644
index 5acf285d06..0000000000
--- a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-must-call-super/options.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "throws": "missing super() call in constructor",
-  "plugins": ["transform-classes"]
-}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-falsey/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-falsey/expected.js
index d4302c852a..8f91a1a798 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-falsey/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-falsey/expected.js
@@ -6,7 +6,7 @@ function (_Base) {
   function Child() {
     var _this;
 
-    return false || _this;
+    return false || babelHelpers.assertThisInitialized(_this);
   }
 
   return Child;
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-object/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-object/expected.js
index c1f860fad0..9d6464d2f2 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-object/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/loose/derived-constructor-no-super-return-object/expected.js
@@ -6,7 +6,7 @@ function (_Base) {
   function Child() {
     var _this;
 
-    return {} || _this;
+    return {} || babelHelpers.assertThisInitialized(_this);
   }
 
   return Child;
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/regression/3028/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/regression/3028/expected.js
index aa11c0529d..2205f40bce 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/regression/3028/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/regression/3028/expected.js
@@ -21,7 +21,7 @@ function (_b) {
     _this = babelHelpers.possibleConstructorReturn(this, (a1.__proto__ || Object.getPrototypeOf(a1)).call(this));
 
     _this.x = function () {
-      return _this;
+      return babelHelpers.assertThisInitialized(_this);
     };
 
     return _this;
@@ -42,7 +42,7 @@ function (_b2) {
     _this2 = babelHelpers.possibleConstructorReturn(this, (a2.__proto__ || Object.getPrototypeOf(a2)).call(this));
 
     _this2.x = function () {
-      return _this2;
+      return babelHelpers.assertThisInitialized(_this2);
     };
 
     return _this2;
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/regression/T7537/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/regression/T7537/expected.js
index 1a7251e480..dc8a3c6389 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/regression/T7537/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/regression/T7537/expected.js
@@ -1,6 +1,6 @@
 function _typeof(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof(obj); }
 
-function _possibleConstructorReturn(self, call) { if (call && (_typeof(call) === "object" || typeof call === "function")) { return call; } if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+function _possibleConstructorReturn(self, call) { if (call && (_typeof(call) === "object" || typeof call === "function")) { return call; } if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
 
 function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
 
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-class/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-class/expected.js
index 94d13bbaf2..f79a960451 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-class/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-class/expected.js
@@ -11,12 +11,12 @@ function (_Foo) {
     babelHelpers.classCallCheck(this, Test);
     woops.super.test();
     _this = babelHelpers.possibleConstructorReturn(this, (Test.__proto__ || Object.getPrototypeOf(Test)).call(this));
-    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this).call(_this);
+    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this)).call(_this);
     _this = babelHelpers.possibleConstructorReturn(this, (Test.__proto__ || Object.getPrototypeOf(Test)).apply(this, arguments));
     _this = babelHelpers.possibleConstructorReturn(this, (_ref = Test.__proto__ || Object.getPrototypeOf(Test)).call.apply(_ref, [this, "test"].concat(Array.prototype.slice.call(arguments))));
-    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this).apply(_this, arguments);
+    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this)).apply(_this, arguments);
 
-    (_babelHelpers$get = babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this)).call.apply(_babelHelpers$get, [_this, "test"].concat(Array.prototype.slice.call(arguments)));
+    (_babelHelpers$get = babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this))).call.apply(_babelHelpers$get, [_this, "test"].concat(Array.prototype.slice.call(arguments)));
 
     return _this;
   }
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-properties/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-properties/expected.js
index 3c2d63221d..91f538dcf2 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-properties/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/accessing-super-properties/expected.js
@@ -8,8 +8,8 @@ function (_Foo) {
 
     babelHelpers.classCallCheck(this, Test);
     _this = babelHelpers.possibleConstructorReturn(this, (Test.__proto__ || Object.getPrototypeOf(Test)).call(this));
-    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this);
-    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this).whatever;
+    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this));
+    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this)).whatever;
     return _this;
   }
 
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/calling-super-properties/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/calling-super-properties/expected.js
index dc5fa2853e..fe64ce3646 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/calling-super-properties/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/calling-super-properties/expected.js
@@ -8,8 +8,8 @@ function (_Foo) {
 
     babelHelpers.classCallCheck(this, Test);
     _this = babelHelpers.possibleConstructorReturn(this, (Test.__proto__ || Object.getPrototypeOf(Test)).call(this));
-    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this).whatever();
-    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", _this).call(_this);
+    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this)).whatever();
+    babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "test", babelHelpers.assertThisInitialized(_this)).call(_this);
     return _this;
   }
 
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/actual.js
new file mode 100644
index 0000000000..985f12206f
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/actual.js
@@ -0,0 +1,5 @@
+class Foo extends Bar {
+  constructor() {
+    if (eval("false")) super();
+  }
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/exec.js
new file mode 100644
index 0000000000..b28eabdab7
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    if (eval("false")) super();
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/expected.js
new file mode 100644
index 0000000000..bd43f1f6c5
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-2/expected.js
@@ -0,0 +1,15 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+    if (eval("false")) _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+    return babelHelpers.possibleConstructorReturn(_this);
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/actual.js
new file mode 100644
index 0000000000..c6473d67ca
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/actual.js
@@ -0,0 +1,6 @@
+class Foo extends Bar {
+  constructor() {
+    const fn = () => super();
+    fn();
+  }
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/exec.js
new file mode 100644
index 0000000000..b5546d3fd1
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/exec.js
@@ -0,0 +1,10 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    const fn = () => super();
+    fn();
+  }
+}
+
+new Foo();
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/expected.js
new file mode 100644
index 0000000000..5ab73330a4
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-3/expected.js
@@ -0,0 +1,18 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+
+    var fn = () => _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+
+    fn();
+    return babelHelpers.possibleConstructorReturn(_this);
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/actual.js
new file mode 100644
index 0000000000..0ea2e049fa
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/actual.js
@@ -0,0 +1,5 @@
+class Foo extends Bar {
+  constructor() {
+    const fn = () => super();
+  }
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/exec.js
new file mode 100644
index 0000000000..032b3293f3
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    const fn = () => super();
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/expected.js
new file mode 100644
index 0000000000..99b2cd7793
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super-4/expected.js
@@ -0,0 +1,17 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+
+    var fn = () => _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+
+    return babelHelpers.possibleConstructorReturn(_this);
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/exec.js
new file mode 100644
index 0000000000..b4aedfd3f5
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/expected.js
new file mode 100644
index 0000000000..d1029e22e3
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/expected.js
@@ -0,0 +1,14 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+    return babelHelpers.possibleConstructorReturn(_this);
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/options.json
deleted file mode 100644
index 5acf285d06..0000000000
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/derived-constructor-must-call-super/options.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "throws": "missing super() call in constructor",
-  "plugins": ["transform-classes"]
-}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-function-fallback/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-function-fallback/expected.js
index baca2fdc01..a1a0e6294a 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-function-fallback/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-function-fallback/expected.js
@@ -1,4 +1,4 @@
 var Test = function Test() {
   babelHelpers.classCallCheck(this, Test);
-  babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "hasOwnProperty", this).call(this, "test");
+  babelHelpers.get(Test.prototype.__proto__ || Object.getPrototypeOf(Test.prototype), "hasOwnProperty", babelHelpers.assertThisInitialized(this)).call(this, "test");
 };
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/exec.js
new file mode 100644
index 0000000000..32af08bde9
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    super.foo(super());
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/expected.js
new file mode 100644
index 0000000000..e019eadfd9
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/expected.js
@@ -0,0 +1,27 @@
+function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
+
+function _possibleConstructorReturn(self, call) { if (call && (typeof call === "object" || typeof call === "function")) { return call; } if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
+function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
+
+function _get(object, property, receiver) { if (object === null) object = Function.prototype; var desc = Object.getOwnPropertyDescriptor(object, property); if (desc === undefined) { var parent = Object.getPrototypeOf(object); if (parent === null) { return undefined; } else { return _get(parent, property, receiver); } } else if ("value" in desc) { return desc.value; } else { var getter = desc.get; if (getter === undefined) { return undefined; } return getter.call(receiver); } }
+
+function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  _inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    _classCallCheck(this, Foo);
+
+    _get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "foo", _assertThisInitialized(_this)).call(_this, _this = _possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this)));
+
+    return _this;
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/options.json
index 31d4d114ab..5d03380e6f 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/options.json
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super-inline/options.json
@@ -1,4 +1,3 @@
 {
-  "throws": "'super.*' is not allowed before super()",
-  "plugins": ["transform-classes"]
+  "plugins": ["transform-classes", "transform-block-scoping"]
 }
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/exec.js
new file mode 100644
index 0000000000..bccb02b6b4
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/exec.js
@@ -0,0 +1,10 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    super.foo();
+    super();
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/expected.js
new file mode 100644
index 0000000000..854033398b
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/expected.js
@@ -0,0 +1,27 @@
+function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
+
+function _possibleConstructorReturn(self, call) { if (call && (typeof call === "object" || typeof call === "function")) { return call; } if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
+function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
+
+function _get(object, property, receiver) { if (object === null) object = Function.prototype; var desc = Object.getOwnPropertyDescriptor(object, property); if (desc === undefined) { var parent = Object.getPrototypeOf(object); if (parent === null) { return undefined; } else { return _get(parent, property, receiver); } } else if ("value" in desc) { return desc.value; } else { var getter = desc.get; if (getter === undefined) { return undefined; } return getter.call(receiver); } }
+
+function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  _inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    _classCallCheck(this, Foo);
+
+    _get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "foo", _assertThisInitialized(_this)).call(_this);
+
+    return _this = _possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/options.json
index 31d4d114ab..5d03380e6f 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/options.json
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-bare-super/options.json
@@ -1,4 +1,3 @@
 {
-  "throws": "'super.*' is not allowed before super()",
-  "plugins": ["transform-classes"]
+  "plugins": ["transform-classes", "transform-block-scoping"]
 }
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/actual.js
index 1d570b180f..e3b40c34f1 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/actual.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/actual.js
@@ -1,6 +1,6 @@
 class Foo extends Bar {
   constructor() {
-    const t = () => super.test()
+    var t = () => super.test()
     super.foo();
     super();
   }
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/exec.js
new file mode 100644
index 0000000000..95a7339037
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/exec.js
@@ -0,0 +1,13 @@
+class Bar {
+  test() {}
+}
+
+class Foo extends Bar {
+  constructor() {
+    const t = () => super.test()
+    t();
+    super();
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/expected.js
new file mode 100644
index 0000000000..248f97f717
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/expected.js
@@ -0,0 +1,18 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+
+    var t = () => babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "test", babelHelpers.assertThisInitialized(_this)).call(_this);
+
+    babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "foo", babelHelpers.assertThisInitialized(_this)).call(_this);
+    return _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/options.json
index 450ed0282e..111b0a6091 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/options.json
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-2/options.json
@@ -1,4 +1,3 @@
 {
-  "throws": "'super.*' is not allowed before super()",
-  "plugins": ["external-helpers", "transform-classes"]
+  "plugins": ["external-helpers", "transform-classes", "transform-block-scoping"]
 }
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/actual.js
new file mode 100644
index 0000000000..29c1f5ac05
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/actual.js
@@ -0,0 +1,7 @@
+class Foo extends Bar {
+  constructor() {
+    const t = () => super.test()
+    super();
+    t();
+  }
+}
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/exec.js
new file mode 100644
index 0000000000..cb85303d3d
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/exec.js
@@ -0,0 +1,13 @@
+class Bar {
+  test() {}
+}
+
+class Foo extends Bar {
+  constructor() {
+    const t = () => super.test()
+    super();
+    t();
+  }
+}
+
+new Foo();
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/expected.js
new file mode 100644
index 0000000000..a856f88fbb
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/expected.js
@@ -0,0 +1,19 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+
+    var t = () => babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "test", babelHelpers.assertThisInitialized(_this)).call(_this);
+
+    _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+    t();
+    return _this;
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/options.json
new file mode 100644
index 0000000000..111b0a6091
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda-3/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["external-helpers", "transform-classes", "transform-block-scoping"]
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/exec.js
new file mode 100644
index 0000000000..3a2dad5f20
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/exec.js
@@ -0,0 +1,12 @@
+class Bar {
+  test() {}
+}
+
+class Foo extends Bar {
+  constructor() {
+    const t = () => super.test()
+    super();
+  }
+}
+
+new Foo();
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/expected.js
index d794d9f873..e973f819b9 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-before-in-lambda/expected.js
@@ -8,7 +8,7 @@ function (_Bar) {
 
     babelHelpers.classCallCheck(this, Foo);
 
-    var t = () => babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "test", _this).call(_this);
+    var t = () => babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "test", babelHelpers.assertThisInitialized(_this)).call(_this);
 
     return _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
   }
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-in-prop-exression/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-in-prop-exression/expected.js
index ff8910b032..9249a2256e 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-in-prop-exression/expected.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/super-reference-in-prop-exression/expected.js
@@ -7,7 +7,7 @@ function (_Bar) {
     var _this;
 
     babelHelpers.classCallCheck(this, Foo);
-    babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), (_this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this))).method, _this).call(_this);
+    babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), (_this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this))).method, babelHelpers.assertThisInitialized(_this)).call(_this);
     return _this;
   }
 
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/exec.js
new file mode 100644
index 0000000000..8cc0a836a1
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    super(this);
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/expected.js
new file mode 100644
index 0000000000..eacbb60486
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/expected.js
@@ -0,0 +1,14 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+    return _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this, babelHelpers.assertThisInitialized(_this)));
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/options.json
deleted file mode 100644
index 1127f3cba4..0000000000
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-2/options.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "throws": "'this' is not allowed before super()",
-  "plugins": ["transform-classes"]
-}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/actual.js
new file mode 100644
index 0000000000..966c4b9e78
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/actual.js
@@ -0,0 +1,7 @@
+class Foo extends Bar {
+  constructor() {
+    const fn = () => this;
+    fn();
+    super();
+  }
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/exec.js
new file mode 100644
index 0000000000..80c1b94f54
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/exec.js
@@ -0,0 +1,11 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    const fn = () => this;
+    fn();
+    super();
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/expected.js
new file mode 100644
index 0000000000..ee5d13b48e
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-3/expected.js
@@ -0,0 +1,18 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+
+    var fn = () => babelHelpers.assertThisInitialized(_this);
+
+    fn();
+    return _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/actual.js
new file mode 100644
index 0000000000..41172aeba7
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/actual.js
@@ -0,0 +1,7 @@
+class Foo extends Bar {
+  constructor() {
+    const fn = () => this;
+    super();
+    fn();
+  }
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/exec.js
new file mode 100644
index 0000000000..fd74386694
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/exec.js
@@ -0,0 +1,11 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    const fn = () => this;
+    super();
+    fn();
+  }
+}
+
+new Foo();
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/expected.js
new file mode 100644
index 0000000000..42144392f3
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-4/expected.js
@@ -0,0 +1,19 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+
+    var fn = () => babelHelpers.assertThisInitialized(_this);
+
+    _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+    fn();
+    return _this;
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/actual.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/actual.js
new file mode 100644
index 0000000000..3011d5d39a
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/actual.js
@@ -0,0 +1,5 @@
+class Foo extends Bar {
+  constructor() {
+    Foo[this];
+  }
+}
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/exec.js
new file mode 100644
index 0000000000..af632c07c4
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/exec.js
@@ -0,0 +1,9 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    Foo[this];
+  }
+}
+
+assert.throws(() => new Foo(), /this hasn't been initialised/);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/expected.js
new file mode 100644
index 0000000000..ef448dd71d
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes-5/expected.js
@@ -0,0 +1,15 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+    Foo[babelHelpers.assertThisInitialized(_this)];
+    return babelHelpers.possibleConstructorReturn(_this);
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/exec.js
new file mode 100644
index 0000000000..08de38754b
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/exec.js
@@ -0,0 +1,10 @@
+class Bar {}
+
+class Foo extends Bar {
+  constructor() {
+    this.foo = "bar";
+    super();
+  }
+}
+
+assert.throws(() => new Foo());
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/expected.js b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/expected.js
new file mode 100644
index 0000000000..b505f250e4
--- /dev/null
+++ b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/expected.js
@@ -0,0 +1,15 @@
+var Foo =
+/*#__PURE__*/
+function (_Bar) {
+  babelHelpers.inherits(Foo, _Bar);
+
+  function Foo() {
+    var _this;
+
+    babelHelpers.classCallCheck(this, Foo);
+    _this.foo = "bar";
+    return _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
+  }
+
+  return Foo;
+}(Bar);
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/options.json b/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/options.json
deleted file mode 100644
index 1127f3cba4..0000000000
--- a/packages/babel-plugin-transform-classes/test/fixtures/spec/this-not-allowed-before-super-in-derived-classes/options.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "throws": "'this' is not allowed before super()",
-  "plugins": ["transform-classes"]
-}
diff --git a/packages/babel-plugin-transform-parameters/test/fixtures/regression/6057-expanded/expected.js b/packages/babel-plugin-transform-parameters/test/fixtures/regression/6057-expanded/expected.js
index 9c03b40d90..c3554cc0ec 100644
--- a/packages/babel-plugin-transform-parameters/test/fixtures/regression/6057-expanded/expected.js
+++ b/packages/babel-plugin-transform-parameters/test/fixtures/regression/6057-expanded/expected.js
@@ -19,10 +19,12 @@ function _defineProperties(target, props) { for (var i = 0; i < props.length; i+
 
 function _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); return Constructor; }
 
-function _possibleConstructorReturn(self, call) { if (call && (_typeof(call) === "object" || typeof call === "function")) { return call; } if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+function _possibleConstructorReturn(self, call) { if (call && (_typeof(call) === "object" || typeof call === "function")) { return call; } if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
 
 function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }
 
+function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }
+
 var App =
 /*#__PURE__*/
 function (_Component) {
@@ -39,7 +41,7 @@ function (_Component) {
       args[_key] = arguments[_key];
     }
 
-    return _possibleConstructorReturn(_this, (_temp = _this = _possibleConstructorReturn(this, (_ref = App.__proto__ || Object.getPrototypeOf(App)).call.apply(_ref, [this].concat(args))), Object.defineProperty(_this, "exportType", {
+    return _possibleConstructorReturn(_this, (_temp = _this = _possibleConstructorReturn(this, (_ref = App.__proto__ || Object.getPrototypeOf(App)).call.apply(_ref, [this].concat(args))), Object.defineProperty(_assertThisInitialized(_this), "exportType", {
       configurable: true,
       enumerable: true,
       writable: true,