diff --git a/packages/babel-helpers/src/helpers.js b/packages/babel-helpers/src/helpers.js
index 3c5194ac11..705d607f45 100644
--- a/packages/babel-helpers/src/helpers.js
+++ b/packages/babel-helpers/src/helpers.js
@@ -377,6 +377,14 @@ helpers.inherits = template(`
   })
 `);
 
+helpers.inheritsLoose = template(`
+  (function (subClass, superClass) {
+    subClass.prototype = Object.create(superClass.prototype);
+    subClass.prototype.constructor = subClass;
+    subClass.__proto__ = superClass;
+  })
+`);
+
 helpers.instanceof = template(`
   (function (left, right) {
     if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) {
diff --git a/packages/babel-plugin-transform-es2015-classes/src/vanilla.js b/packages/babel-plugin-transform-es2015-classes/src/vanilla.js
index 42d20bf368..52e5153e91 100644
--- a/packages/babel-plugin-transform-es2015-classes/src/vanilla.js
+++ b/packages/babel-plugin-transform-es2015-classes/src/vanilla.js
@@ -127,13 +127,15 @@ export default class ClassTransformer {
     //
     this.buildBody();
 
-    // make sure this class isn't directly called
-    constructorBody.body.unshift(t.expressionStatement(t.callExpression(
-      file.addHelper("classCallCheck"), [
-        t.thisExpression(),
-        this.classRef,
-      ]
-    )));
+    // make sure this class isn't directly called (with A() instead new A())
+    if (!this.isLoose) {
+      constructorBody.body.unshift(t.expressionStatement(t.callExpression(
+        file.addHelper("classCallCheck"), [
+          t.thisExpression(),
+          this.classRef,
+        ]
+      )));
+    }
 
     body = body.concat(this.staticPropBody.map((fn) => fn(this.classRef)));
 
@@ -374,10 +376,16 @@ export default class ClassTransformer {
       );
     }
 
-    let call = t.callExpression(
-      this.file.addHelper("possibleConstructorReturn"),
-      [t.thisExpression(), bareSuperNode]
-    );
+    let call;
+
+    if (this.isLoose) {
+      call = t.logicalExpression("||", bareSuperNode, t.thisExpression());
+    } else {
+      call = t.callExpression(
+        this.file.addHelper("possibleConstructorReturn"),
+        [t.thisExpression(), bareSuperNode]
+      );
+    }
 
     const bareSuperAfter = this.bareSuperAfter.map((fn) => fn(thisRef));
 
@@ -446,10 +454,18 @@ export default class ClassTransformer {
       thisPath.replaceWith(thisRef);
     }
 
-    const wrapReturn = (returnArg) => t.callExpression(
-      this.file.addHelper("possibleConstructorReturn"),
-      [thisRef].concat(returnArg || [])
-    );
+    let wrapReturn;
+
+    if (this.isLoose) {
+      wrapReturn = (returnArg) => {
+        return returnArg ? t.logicalExpression("||", returnArg, thisRef) : thisRef;
+      };
+    } else {
+      wrapReturn = (returnArg) => t.callExpression(
+        this.file.addHelper("possibleConstructorReturn"),
+        [thisRef].concat(returnArg || [])
+      );
+    }
 
     // if we have a return as the last node in the body then we've already caught that
     // return
@@ -546,7 +562,7 @@ export default class ClassTransformer {
     // any properties can be assigned to the prototype.
     this.pushedInherits = true;
     this.body.unshift(t.expressionStatement(t.callExpression(
-      this.file.addHelper("inherits"),
+      this.isLoose ? this.file.addHelper("inheritsLoose") : this.file.addHelper("inherits"),
       [this.classRef, this.superName]
     )));
   }
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/class/actual.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/class/actual.js
new file mode 100644
index 0000000000..a869c28495
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/class/actual.js
@@ -0,0 +1 @@
+class A {}
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/class/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/class/expected.js
new file mode 100644
index 0000000000..8311a6c3db
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/class/expected.js
@@ -0,0 +1 @@
+let A = function A() {};
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/options.json b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/options.json
new file mode 100644
index 0000000000..cad18de53d
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/options.json
@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    ["transform-es2015-classes", {
+      "loose": true
+    }]
+  ]
+}
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/actual.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/actual.js
new file mode 100644
index 0000000000..9da66478b2
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/actual.js
@@ -0,0 +1,11 @@
+class A {
+  constructor() {
+    console.log('a');
+  }
+}
+
+class B {
+  b() {
+    console.log('b');
+  }
+}
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/expected.js
new file mode 100644
index 0000000000..e0e9ee4b85
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/expected.js
@@ -0,0 +1,13 @@
+let A = function A() {
+  console.log('a');
+};
+
+let B = function () {
+  function B() {}
+
+  B.prototype.b = function b() {
+    console.log('b');
+  };
+
+  return B;
+}();
\ No newline at end of file
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/actual.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/actual.js
new file mode 100644
index 0000000000..76bb1ebddf
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/actual.js
@@ -0,0 +1,8 @@
+class B {}
+
+class A extends B {
+  constructor(track) {
+    if (track !== undefined) super(track);
+    else super();
+  }
+}
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js
new file mode 100644
index 0000000000..2ba8ea8a73
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js
@@ -0,0 +1,18 @@
+function _inheritsLoose(subClass, superClass) { subClass.prototype = Object.create(superClass.prototype); subClass.prototype.constructor = subClass; subClass.__proto__ = superClass; }
+
+let B = function B() {};
+
+let A = function (_B) {
+  _inheritsLoose(A, _B);
+
+  function A(track) {
+    if (track !== undefined) {
+      var _this = _B.call(this, track) || this;
+    } else {
+      var _this = _B.call(this) || this;
+    }
+    return _this;
+  }
+
+  return A;
+}(B);
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-class/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-class/expected.js
index f837c9c172..697df5c608 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-class/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-class/expected.js
@@ -1,20 +1,18 @@
 var Test = function (_Foo) {
-  babelHelpers.inherits(Test, _Foo);
+  babelHelpers.inheritsLoose(Test, _Foo);
 
   function Test() {
     var _Foo$prototype$test, _Foo$prototype$test2;
 
-    babelHelpers.classCallCheck(this, Test);
-
     woops.super.test();
 
-    var _this = babelHelpers.possibleConstructorReturn(this, _Foo.call(this));
+    var _this = _Foo.call(this) || this;
 
     _Foo.prototype.test.call(_this);
 
-    var _this = babelHelpers.possibleConstructorReturn(this, _Foo.apply(this, arguments));
+    var _this = _Foo.apply(this, arguments) || this;
 
-    var _this = babelHelpers.possibleConstructorReturn(this, _Foo.call.apply(_Foo, [this, "test"].concat(Array.prototype.slice.call(arguments))));
+    var _this = _Foo.call.apply(_Foo, [this, "test"].concat(Array.prototype.slice.call(arguments))) || this;
 
     (_Foo$prototype$test = _Foo.prototype.test).call.apply(_Foo$prototype$test, [_this].concat(Array.prototype.slice.call(arguments)));
     (_Foo$prototype$test2 = _Foo.prototype.test).call.apply(_Foo$prototype$test2, [_this, "test"].concat(Array.prototype.slice.call(arguments)));
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-properties/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-properties/expected.js
index b1da9bd99f..03969d0f8d 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-properties/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/accessing-super-properties/expected.js
@@ -1,10 +1,8 @@
 var Test = function (_Foo) {
-  babelHelpers.inherits(Test, _Foo);
+  babelHelpers.inheritsLoose(Test, _Foo);
 
   function Test() {
-    babelHelpers.classCallCheck(this, Test);
-
-    var _this = babelHelpers.possibleConstructorReturn(this, _Foo.call(this));
+    var _this = _Foo.call(this) || this;
 
     _Foo.prototype.test;
     _Foo.prototype.test.whatever;
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/calling-super-properties/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/calling-super-properties/expected.js
index 25bdf6a1c3..3ef936da91 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/calling-super-properties/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/calling-super-properties/expected.js
@@ -1,10 +1,8 @@
 var Test = function (_Foo) {
-  babelHelpers.inherits(Test, _Foo);
+  babelHelpers.inheritsLoose(Test, _Foo);
 
   function Test() {
-    babelHelpers.classCallCheck(this, Test);
-
-    var _this = babelHelpers.possibleConstructorReturn(this, _Foo.call(this));
+    var _this = _Foo.call(this) || this;
 
     _Foo.prototype.test.whatever();
     _Foo.prototype.test.call(_this);
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/constructor-order/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/constructor-order/expected.js
index 4ebd527994..be7df63f56 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/constructor-order/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/constructor-order/expected.js
@@ -6,8 +6,6 @@ var x = function () {
   };
 
   function x() {
-    babelHelpers.classCallCheck(this, x);
-
     4;
     5;
     6;
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/literal-key/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/literal-key/expected.js
index 9d78574423..126cb3ecde 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/literal-key/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/literal-key/expected.js
@@ -1,7 +1,5 @@
 var Foo = function () {
-  function Foo() {
-    babelHelpers.classCallCheck(this, Foo);
-  }
+  function Foo() {}
 
   Foo.prototype["bar"] = function bar() {};
 
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-return-type-annotation/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-return-type-annotation/expected.js
index c426f3b6ac..513dccbcdf 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-return-type-annotation/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-return-type-annotation/expected.js
@@ -1,8 +1,6 @@
 // @flow
 var C = function () {
-  function C() {
-    babelHelpers.classCallCheck(this, C);
-  }
+  function C() {}
 
   C.prototype.m = function m(x: number): string {
     return 'a';
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/options.json b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/options.json
index 5ba1a293bd..14e2e6ea02 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/options.json
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/options.json
@@ -1,3 +1,9 @@
 {
-  "plugins": ["external-helpers", "transform-es2015-function-name", ["transform-es2015-classes", { "loose": true }], "transform-es2015-spread", "transform-es2015-block-scoping"]
+  "plugins": [
+    "external-helpers",
+    "transform-es2015-function-name",
+    ["transform-es2015-classes", { "loose": true }],
+    ["transform-es2015-spread", { "loose": true }],
+    "transform-es2015-block-scoping"
+  ]
 }
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class-id-member-expression/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class-id-member-expression/expected.js
index e03b4f885c..fad14f464e 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class-id-member-expression/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class-id-member-expression/expected.js
@@ -1,20 +1,18 @@
 var BaseController = function (_Chaplin$Controller) {
-  babelHelpers.inherits(BaseController, _Chaplin$Controller);
+  babelHelpers.inheritsLoose(BaseController, _Chaplin$Controller);
 
   function BaseController() {
-    babelHelpers.classCallCheck(this, BaseController);
-    return babelHelpers.possibleConstructorReturn(this, _Chaplin$Controller.apply(this, arguments));
+    return _Chaplin$Controller.apply(this, arguments) || this;
   }
 
   return BaseController;
 }(Chaplin.Controller);
 
 var BaseController2 = function (_Chaplin$Controller$A) {
-  babelHelpers.inherits(BaseController2, _Chaplin$Controller$A);
+  babelHelpers.inheritsLoose(BaseController2, _Chaplin$Controller$A);
 
   function BaseController2() {
-    babelHelpers.classCallCheck(this, BaseController2);
-    return babelHelpers.possibleConstructorReturn(this, _Chaplin$Controller$A.apply(this, arguments));
+    return _Chaplin$Controller$A.apply(this, arguments) || this;
   }
 
   return BaseController2;
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class/expected.js
index dd6df765b8..d9e146771b 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-class/expected.js
@@ -1,9 +1,8 @@
 var Test = function (_Foo) {
-  babelHelpers.inherits(Test, _Foo);
+  babelHelpers.inheritsLoose(Test, _Foo);
 
   function Test() {
-    babelHelpers.classCallCheck(this, Test);
-    return babelHelpers.possibleConstructorReturn(this, _Foo.apply(this, arguments));
+    return _Foo.apply(this, arguments) || this;
   }
 
   return Test;
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-function-fallback/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-function-fallback/expected.js
index 1f23d494a8..090bb67b1b 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-function-fallback/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/super-function-fallback/expected.js
@@ -1,5 +1,3 @@
 var Test = function Test() {
-  babelHelpers.classCallCheck(this, Test);
-
   Function.prototype.hasOwnProperty.call(this, "test");
 };
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/expected.js
index 3a32ac177a..74bafa673b 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/expected.js
@@ -1,11 +1,7 @@
 "use strict";
 
-function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
-
 var Example = function () {
-  function Example() {
-    _classCallCheck(this, Example);
-  }
+  function Example() {}
 
   Example.prototype.test1 = async function test1() {
     await Promise.resolve(2);
diff --git a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-loose-return-type-annotation/expected.js b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-loose-return-type-annotation/expected.js
index 5df0023a18..8fd3bee001 100644
--- a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-loose-return-type-annotation/expected.js
+++ b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-loose-return-type-annotation/expected.js
@@ -2,13 +2,11 @@
 
 // @flow
 var C = function () {
-  function C() {
-    babelHelpers.classCallCheck(this, C);
-  }
+  function C() {}
 
   C.prototype.m = function m(x /*: number*/) /*: string*/ {
     return 'a';
   };
 
   return C;
-}();
\ No newline at end of file
+}();
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-loose-return-type-annotation/expected.js b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-loose-return-type-annotation/expected.js
index b12c969201..d3f42768b7 100644
--- a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-loose-return-type-annotation/expected.js
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-loose-return-type-annotation/expected.js
@@ -1,13 +1,11 @@
 "use strict";
 
 var C = function () {
-  function C() {
-    babelHelpers.classCallCheck(this, C);
-  }
+  function C() {}
 
   C.prototype.m = function m(x) {
     return 'a';
   };
 
   return C;
-}();
\ No newline at end of file
+}();