diff --git a/lib/6to5/transformation/modules/amd.js b/lib/6to5/transformation/modules/amd.js
index 3940c9d18d..6d06ddbe46 100644
--- a/lib/6to5/transformation/modules/amd.js
+++ b/lib/6to5/transformation/modules/amd.js
@@ -87,7 +87,11 @@ AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
   var key = t.getSpecifierName(specifier);
   var ref = this._push(node);
 
-  if (t.isImportBatchSpecifier(specifier)) {
+  if (_.contains(this.file.dynamicImports, node)) {
+    // Prevent unnecessary renaming of dynamic imports.
+    this.ids[node.source.value] = key;
+    return;
+  } else if (t.isImportBatchSpecifier(specifier)) {
     // import * as bar from "foo";
   } else if (t.isSpecifierDefault(specifier) && !this.noInteropRequire) {
     // import foo from "foo";
diff --git a/lib/6to5/transformation/modules/common.js b/lib/6to5/transformation/modules/common.js
index 8e6044f2e9..73653c8d04 100644
--- a/lib/6to5/transformation/modules/common.js
+++ b/lib/6to5/transformation/modules/common.js
@@ -6,6 +6,7 @@ var DefaultFormatter = require("./_default");
 var traverse         = require("../../traverse");
 var util             = require("../../util");
 var t                = require("../../types");
+var _                = require("lodash");
 
 function CommonJSFormatter(file) {
   DefaultFormatter.apply(this, arguments);
@@ -26,13 +27,13 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
 
   // import foo from "foo";
   if (t.isSpecifierDefault(specifier)) {
-    nodes.push(t.variableDeclaration("var", [
-      t.variableDeclarator(variableName,
-        t.callExpression(this.file.addHelper("interop-require"), [util.template("require", {
-          MODULE_NAME: node.source
-        })])
-      )
-    ]));
+    var ref = util.template("require", {
+      MODULE_NAME: node.source
+    });
+    if (!_.contains(this.file.dynamicImports, node)) {
+      ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
+    }
+    nodes.push(t.variableDeclaration("var", [t.variableDeclarator(variableName, ref)]));
   } else {
     if (specifier.type === "ImportBatchSpecifier") {
       // import * as bar from "foo";
diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index a98b0fe820..5a8d63e74d 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -96,7 +96,7 @@ _.each({
   _moduleFormatter:          require("./transformers/_module-formatter"),
 
   typeofSymbol:              require("./transformers/optional-typeof-symbol"),
-  coreAliasing:              require("./transformers/optional-core-aliasing"),
+  selfContained:             require("./transformers/optional-self-contained"),
   undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
   undeclaredVariableCheck:   require("./transformers/optional-undeclared-variable-check"),
 
diff --git a/lib/6to5/transformation/transformers/optional-core-aliasing.js b/lib/6to5/transformation/transformers/optional-self-contained.js
similarity index 81%
rename from lib/6to5/transformation/transformers/optional-core-aliasing.js
rename to lib/6to5/transformation/transformers/optional-self-contained.js
index 90bb4621a7..5d4ec3ff1e 100644
--- a/lib/6to5/transformation/transformers/optional-core-aliasing.js
+++ b/lib/6to5/transformation/transformers/optional-self-contained.js
@@ -23,7 +23,9 @@ exports.optional = true;
 
 exports.ast = {
   enter: function (ast, file) {
-    file._coreId = file.addImport("core-js/library", "core");
+    file.opts.runtime = file.addImport("6to5-runtime/helpers", "to5Runtime").name;
+    file._coreId = file.addImport("6to5-runtime/core-js", "core");
+    file._regeneratorId = file.addImport("6to5-runtime/regenerator", "regeneratorRuntime");
   },
 
   exit: function (ast, file) {
@@ -67,3 +69,9 @@ exports.ast = {
     });
   }
 };
+
+exports.Identifier = function (node, parent, scope, context, file) {
+  if (node.name === "regeneratorRuntime" && t.isReferenced(node, parent)) {
+    node.name = file._regeneratorId;
+  }
+};
diff --git a/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js b/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js
index 13943a98de..ed68858b19 100644
--- a/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js
+++ b/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js
@@ -1,10 +1,6 @@
 "use strict";
 
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _bluebird = _interopRequire(require("bluebird"));
+var _bluebird = require("bluebird");
 
 var foo = _bluebird.coroutine(function* () {
   var wat = yield bar();
diff --git a/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js b/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js
index 9b200b29f0..c5dbaaf5d1 100644
--- a/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js
+++ b/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js
@@ -1,10 +1,6 @@
 "use strict";
 
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _bluebird = _interopRequire(require("bluebird"));
+var _bluebird = require("bluebird");
 
 var foo = _bluebird.coroutine(function* foo() {
   var wat = yield bar();
diff --git a/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js b/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js
deleted file mode 100644
index 7c6e3f9ba2..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js
+++ /dev/null
@@ -1,15 +0,0 @@
-"use strict";
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _core = _interopRequire(require("core-js/library"));
-
-obj.constructor === Object;
-obj.constructor === _core.Promise;
-
-_core.Symbol();
-_core.Symbol("test");
-
-new _core.Map();
diff --git a/test/fixtures/transformation/optional-core-aliasing/es6-destructuring/actual.js b/test/fixtures/transformation/optional-core-aliasing/es6-destructuring/actual.js
deleted file mode 100644
index 10aa8799ed..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/es6-destructuring/actual.js
+++ /dev/null
@@ -1 +0,0 @@
-var [a, [b], [c], d] = ["hello", [", ", "junk"], ["world"]];
diff --git a/test/fixtures/transformation/optional-core-aliasing/es6-destructuring/expected.js b/test/fixtures/transformation/optional-core-aliasing/es6-destructuring/expected.js
deleted file mode 100644
index fc43ff5423..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/es6-destructuring/expected.js
+++ /dev/null
@@ -1,34 +0,0 @@
-"use strict";
-
-var _slicedToArray = function (arr, i) {
-  if (Array.isArray(arr)) {
-    return arr;
-  } else {
-    var _arr = [];
-
-    for (var _iterator = _core.$for.getIterator(arr), _step; !(_step = _iterator.next()).done;) {
-      _arr.push(_step.value);
-
-      if (i && _arr.length === i) break;
-    }
-
-    return _arr;
-  }
-};
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _core = _interopRequire(require("core-js/library"));
-
-var _ref = ["hello", [", ", "junk"], ["world"]];
-
-var a = _ref[0];
-var _ref$1 = _slicedToArray(_ref[1], 1);
-
-var b = _ref$1[0];
-var _ref$2 = _slicedToArray(_ref[2], 1);
-
-var c = _ref$2[0];
-var d = _ref[3];
diff --git a/test/fixtures/transformation/optional-core-aliasing/es6-for-of/expected.js b/test/fixtures/transformation/optional-core-aliasing/es6-for-of/expected.js
deleted file mode 100644
index 3bf1f53a05..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/es6-for-of/expected.js
+++ /dev/null
@@ -1,11 +0,0 @@
-"use strict";
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _core = _interopRequire(require("core-js/library"));
-
-for (var _iterator = _core.$for.getIterator(arr), _step; !(_step = _iterator.next()).done;) {
-  var i = _step.value;
-}
diff --git a/test/fixtures/transformation/optional-core-aliasing/es6-spread/actual.js b/test/fixtures/transformation/optional-core-aliasing/es6-spread/actual.js
deleted file mode 100644
index 5ebb80da66..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/es6-spread/actual.js
+++ /dev/null
@@ -1 +0,0 @@
-var lyrics = ["head", "and", "toes", ...parts];
diff --git a/test/fixtures/transformation/optional-core-aliasing/es6-spread/expected.js b/test/fixtures/transformation/optional-core-aliasing/es6-spread/expected.js
deleted file mode 100644
index 4d00347582..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/es6-spread/expected.js
+++ /dev/null
@@ -1,13 +0,0 @@
-"use strict";
-
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : _core.Array.from(arr);
-};
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _core = _interopRequire(require("core-js/library"));
-
-var lyrics = ["head", "and", "toes"].concat(_toArray(parts));
diff --git a/test/fixtures/transformation/optional-core-aliasing/options.json b/test/fixtures/transformation/optional-core-aliasing/options.json
deleted file mode 100644
index 371b5f0b20..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/options.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "optional": ["coreAliasing"],
-  "experimental": true
-}
diff --git a/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/actual.js b/test/fixtures/transformation/optional-self-contained/aliased-constructors/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-core-aliasing/aliased-constructors/actual.js
rename to test/fixtures/transformation/optional-self-contained/aliased-constructors/actual.js
diff --git a/test/fixtures/transformation/optional-self-contained/aliased-constructors/expected.js b/test/fixtures/transformation/optional-self-contained/aliased-constructors/expected.js
new file mode 100644
index 0000000000..2242afb8f8
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/aliased-constructors/expected.js
@@ -0,0 +1,15 @@
+"use strict";
+
+var _to5Runtime = require("6to5-runtime/helpers");
+
+var _core = require("6to5-runtime/core-js");
+
+var _regeneratorRuntime = require("6to5-runtime/regenerator");
+
+obj.constructor === Object;
+obj.constructor === _core.Promise;
+
+_core.Symbol();
+_core.Symbol("test");
+
+new _core.Map();
diff --git a/test/fixtures/transformation/optional-core-aliasing/es6-for-of/actual.js b/test/fixtures/transformation/optional-self-contained/es6-for-of/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-core-aliasing/es6-for-of/actual.js
rename to test/fixtures/transformation/optional-self-contained/es6-for-of/actual.js
diff --git a/test/fixtures/transformation/optional-self-contained/es6-for-of/expected.js b/test/fixtures/transformation/optional-self-contained/es6-for-of/expected.js
new file mode 100644
index 0000000000..4d781e1d60
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/es6-for-of/expected.js
@@ -0,0 +1,11 @@
+"use strict";
+
+var _to5Runtime = require("6to5-runtime/helpers");
+
+var _core = require("6to5-runtime/core-js");
+
+var _regeneratorRuntime = require("6to5-runtime/regenerator");
+
+for (var _iterator = _core.$for.getIterator(arr), _step; !(_step = _iterator.next()).done;) {
+  var i = _step.value;
+}
diff --git a/test/fixtures/transformation/optional-core-aliasing/es7-array-comprehensions/actual.js b/test/fixtures/transformation/optional-self-contained/es7-array-comprehensions/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-core-aliasing/es7-array-comprehensions/actual.js
rename to test/fixtures/transformation/optional-self-contained/es7-array-comprehensions/actual.js
diff --git a/test/fixtures/transformation/optional-core-aliasing/es7-array-comprehensions/expected.js b/test/fixtures/transformation/optional-self-contained/es7-array-comprehensions/expected.js
similarity index 58%
rename from test/fixtures/transformation/optional-core-aliasing/es7-array-comprehensions/expected.js
rename to test/fixtures/transformation/optional-self-contained/es7-array-comprehensions/expected.js
index 01333ca8f9..374a18cb98 100644
--- a/test/fixtures/transformation/optional-core-aliasing/es7-array-comprehensions/expected.js
+++ b/test/fixtures/transformation/optional-self-contained/es7-array-comprehensions/expected.js
@@ -1,10 +1,10 @@
 "use strict";
 
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
+var _to5Runtime = require("6to5-runtime/helpers");
 
-var _core = _interopRequire(require("core-js/library"));
+var _core = require("6to5-runtime/core-js");
+
+var _regeneratorRuntime = require("6to5-runtime/regenerator");
 
 var arr = (function () {
   var _arr = [];
diff --git a/test/fixtures/transformation/optional-self-contained/full/actual.js b/test/fixtures/transformation/optional-self-contained/full/actual.js
new file mode 100644
index 0000000000..3e8b1bcdbc
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/full/actual.js
@@ -0,0 +1,6 @@
+import foo, * as bar from "someModule";
+
+export const myWord = Symbol("abc");
+export function* giveWord () {
+  yield myWord;
+}
diff --git a/test/fixtures/transformation/optional-self-contained/full/expected.js b/test/fixtures/transformation/optional-self-contained/full/expected.js
new file mode 100644
index 0000000000..2fe954e8df
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/full/expected.js
@@ -0,0 +1,27 @@
+"use strict";
+
+var _to5Runtime = require("6to5-runtime/helpers");
+
+var _core = require("6to5-runtime/core-js");
+
+var _regeneratorRuntime = require("6to5-runtime/regenerator");
+
+var giveWord = _regeneratorRuntime.mark(function giveWord() {
+  return _regeneratorRuntime.wrap(function giveWord$(context$1$0) {
+    while (1) switch (context$1$0.prev = context$1$0.next) {
+      case 0:
+        context$1$0.next = 2;
+        return myWord;
+      case 2:
+      case "end":
+        return context$1$0.stop();
+    }
+  }, giveWord, this);
+});
+
+exports.giveWord = giveWord;
+var foo = _to5Runtime.interopRequire(require("someModule"));
+
+var bar = _to5Runtime.interopRequireWildcard(require("someModule"));
+
+var myWord = exports.myWord = _core.Symbol("abc");
diff --git a/test/fixtures/transformation/optional-self-contained/options.json b/test/fixtures/transformation/optional-self-contained/options.json
new file mode 100644
index 0000000000..079cf304ad
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/options.json
@@ -0,0 +1,4 @@
+{
+  "optional": ["selfContained"],
+  "experimental": true
+}
diff --git a/test/fixtures/transformation/optional-self-contained/regenerator-runtime/actual.js b/test/fixtures/transformation/optional-self-contained/regenerator-runtime/actual.js
new file mode 100644
index 0000000000..ae6cc4d8c8
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/regenerator-runtime/actual.js
@@ -0,0 +1,2 @@
+void function* () {
+};
diff --git a/test/fixtures/transformation/optional-self-contained/regenerator-runtime/expected.js b/test/fixtures/transformation/optional-self-contained/regenerator-runtime/expected.js
new file mode 100644
index 0000000000..e7fa729a14
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/regenerator-runtime/expected.js
@@ -0,0 +1,17 @@
+"use strict";
+
+var _to5Runtime = require("6to5-runtime/helpers");
+
+var _core = require("6to5-runtime/core-js");
+
+var _regeneratorRuntime = require("6to5-runtime/regenerator");
+
+void _regeneratorRuntime.mark(function callee$0$0() {
+  return _regeneratorRuntime.wrap(function callee$0$0$(context$1$0) {
+    while (1) switch (context$1$0.prev = context$1$0.next) {
+      case 0:
+      case "end":
+        return context$1$0.stop();
+    }
+  }, callee$0$0, this);
+});
diff --git a/test/fixtures/transformation/optional-self-contained/runtime-amd/actual.js b/test/fixtures/transformation/optional-self-contained/runtime-amd/actual.js
new file mode 100644
index 0000000000..09493dc9be
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/runtime-amd/actual.js
@@ -0,0 +1 @@
+import foo from "someModule";
diff --git a/test/fixtures/transformation/optional-self-contained/runtime-amd/expected.js b/test/fixtures/transformation/optional-self-contained/runtime-amd/expected.js
new file mode 100644
index 0000000000..292e6b96cf
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/runtime-amd/expected.js
@@ -0,0 +1,5 @@
+define(["exports", "6to5-runtime/helpers", "6to5-runtime/core-js", "6to5-runtime/regenerator", "someModule"], function (exports, _to5Runtime, _core, _regeneratorRuntime, _someModule) {
+  "use strict";
+
+  var foo = _to5Runtime.interopRequire(_someModule);
+});
diff --git a/test/fixtures/transformation/optional-self-contained/runtime-amd/options.json b/test/fixtures/transformation/optional-self-contained/runtime-amd/options.json
new file mode 100644
index 0000000000..b76b119f33
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/runtime-amd/options.json
@@ -0,0 +1,3 @@
+{
+  "modules": "amd"
+}
diff --git a/test/fixtures/transformation/optional-self-contained/runtime-commonjs/actual.js b/test/fixtures/transformation/optional-self-contained/runtime-commonjs/actual.js
new file mode 100644
index 0000000000..9e9515cece
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/runtime-commonjs/actual.js
@@ -0,0 +1 @@
+import * as foo from "someModule";
diff --git a/test/fixtures/transformation/optional-self-contained/runtime-commonjs/expected.js b/test/fixtures/transformation/optional-self-contained/runtime-commonjs/expected.js
new file mode 100644
index 0000000000..d7a8de73f8
--- /dev/null
+++ b/test/fixtures/transformation/optional-self-contained/runtime-commonjs/expected.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var _to5Runtime = require("6to5-runtime/helpers");
+
+var _core = require("6to5-runtime/core-js");
+
+var _regeneratorRuntime = require("6to5-runtime/regenerator");
+
+var foo = _to5Runtime.interopRequireWildcard(require("someModule"));