diff --git a/packages/babel-core/test/api.js b/packages/babel-core/test/api.js
index 99259ce4c1..2be88b495a 100644
--- a/packages/babel-core/test/api.js
+++ b/packages/babel-core/test/api.js
@@ -285,16 +285,7 @@ describe("api", function() {
 
     assert.equal(aliasBaseType, "NumberTypeAnnotation");
 
-    assert.deepEqual(
-      [
-        '"use strict";',
-        "",
-        "var x = function x(y) {",
-        "  return y;",
-        "};",
-      ].join("\n"),
-      result.code,
-    );
+    assert.deepEqual(result.code, "var x = function x(y) {\n  return y;\n};");
 
     // 2. passPerPreset: false
 
@@ -304,16 +295,7 @@ describe("api", function() {
 
     assert.equal(aliasBaseType, null);
 
-    assert.deepEqual(
-      [
-        '"use strict";',
-        "",
-        "var x = function x(y) {",
-        "  return y;",
-        "};",
-      ].join("\n"),
-      result.code,
-    );
+    assert.deepEqual(result.code, "var x = function x(y) {\n  return y;\n};");
   });
 
   it("complex plugin and preset ordering", function() {
diff --git a/packages/babel-core/test/fixtures/transformation/misc/regression-4855/expected.js b/packages/babel-core/test/fixtures/transformation/misc/regression-4855/expected.js
index 31462a08e1..bd646847de 100644
--- a/packages/babel-core/test/fixtures/transformation/misc/regression-4855/expected.js
+++ b/packages/babel-core/test/fixtures/transformation/misc/regression-4855/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var _values = values;
 var _fieldName = fieldName;
 value = _values[_fieldName];
diff --git a/packages/babel-helper-fixtures/src/index.js b/packages/babel-helper-fixtures/src/index.js
index 42324b4237..5e863ba2f0 100644
--- a/packages/babel-helper-fixtures/src/index.js
+++ b/packages/babel-helper-fixtures/src/index.js
@@ -1,3 +1,4 @@
+import assert from "assert";
 import cloneDeep from "lodash/cloneDeep";
 import trimEnd from "lodash/trimEnd";
 import resolve from "try-resolve";
@@ -83,24 +84,46 @@ export default function get(entryLoc): Array<Suite> {
     }
 
     function push(taskName, taskDir) {
-      const actualLocAlias = suiteName + "/" + taskName + "/actual.js";
+      let actualLocAlias = suiteName + "/" + taskName + "/actual.js";
       let expectLocAlias = suiteName + "/" + taskName + "/expected.js";
-      const execLocAlias = suiteName + "/" + taskName + "/exec.js";
+      let execLocAlias = suiteName + "/" + taskName + "/exec.js";
 
-      const actualLoc = taskDir + "/actual.js";
+      let actualLoc = taskDir + "/actual.js";
       let expectLoc = taskDir + "/expected.js";
       let execLoc = taskDir + "/exec.js";
 
-      if (fs.statSync(taskDir).isFile()) {
-        const ext = path.extname(taskDir);
-        if (ext !== ".js" && ext !== ".module.js") return;
+      const hasExecJS = fs.existsSync(execLoc);
+      const hasExecMJS = fs.existsSync(asMJS(execLoc));
+      if (hasExecMJS) {
+        assert(!hasExecJS, `${asMJS(execLoc)}: Found conflicting .js`);
 
-        execLoc = taskDir;
+        execLoc = asMJS(execLoc);
+        execLocAlias = asMJS(execLocAlias);
       }
 
-      if (resolve.relative(expectLoc + "on")) {
-        expectLoc += "on";
-        expectLocAlias += "on";
+      const hasExpectJS = fs.existsSync(expectLoc);
+      const hasExpectMJS = fs.existsSync(asMJS(expectLoc));
+      if (hasExpectMJS) {
+        assert(!hasExpectJS, `${asMJS(expectLoc)}: Found conflicting .js`);
+
+        expectLoc = asMJS(expectLoc);
+        expectLocAlias = asMJS(expectLocAlias);
+      }
+
+      const hasActualJS = fs.existsSync(actualLoc);
+      const hasActualMJS = fs.existsSync(asMJS(actualLoc));
+      if (hasActualMJS) {
+        assert(!hasActualJS, `${asMJS(actualLoc)}: Found conflicting .js`);
+
+        actualLoc = asMJS(actualLoc);
+        actualLocAlias = asMJS(actualLocAlias);
+      }
+
+      if (fs.statSync(taskDir).isFile()) {
+        const ext = path.extname(taskDir);
+        if (ext !== ".js" && ext !== ".mjs") return;
+
+        execLoc = taskDir;
       }
 
       const taskOpts = cloneDeep(suite.options);
@@ -186,6 +209,10 @@ export function multiple(entryLoc, ignore?: Array<string>) {
   return categories;
 }
 
+function asMJS(filepath) {
+  return filepath.replace(/\.js$/, ".mjs");
+}
+
 export function readFile(filename) {
   if (fs.existsSync(filename)) {
     let file = trimEnd(fs.readFileSync(filename, "utf8"));
diff --git a/packages/babel-helper-module-transforms/src/index.js b/packages/babel-helper-module-transforms/src/index.js
index 6d40af3f96..f868c01fc3 100644
--- a/packages/babel-helper-module-transforms/src/index.js
+++ b/packages/babel-helper-module-transforms/src/index.js
@@ -1,3 +1,4 @@
+import assert from "assert";
 import * as t from "babel-types";
 import template from "babel-template";
 import chunk from "lodash/chunk";
@@ -11,6 +12,31 @@ import normalizeAndLoadModuleMetadata, {
 
 export { hasExports, isSideEffectImport };
 
+export function isModule(path: NodePath, requireUnambiguous: boolean = false) {
+  const { sourceType } = path.node;
+  if (sourceType !== "module" && sourceType !== "script") {
+    throw path.buildCodeFrameError(
+      `Unknown sourceType "${sourceType}", cannot transform.`,
+    );
+  }
+
+  const filename = path.hub.file.opts.filename;
+  if (/\.mjs$/.test(filename)) {
+    requireUnambiguous = false;
+  }
+
+  return (
+    path.node.sourceType === "module" &&
+    (!requireUnambiguous || isUnambiguousModule(path))
+  );
+}
+
+// This approach is not ideal. It is here to preserve compatibility for now,
+// but really this should just return true or be deleted.
+function isUnambiguousModule(path) {
+  return path.get("body").some(p => p.isModuleDeclaration());
+}
+
 /**
  * Perform all of the generic ES6 module rewriting needed to handle initial
  * module processing. This function will rewrite the majority of the given
@@ -21,6 +47,9 @@ export function rewriteModuleStatementsAndPrepareHeader(
   path: NodePath,
   { exportName, strict, allowTopLevelThis, strictMode, loose, noInterop },
 ) {
+  assert(isModule(path), "Cannot process module statements in a script");
+  path.node.sourceType = "script";
+
   const meta = normalizeAndLoadModuleMetadata(path, exportName, {
     noInterop,
   });
diff --git a/packages/babel-plugin-transform-class-properties/test/fixtures/general/foobar/expected.js b/packages/babel-plugin-transform-class-properties/test/fixtures/general/foobar/expected.js
index 3532914e26..2865c35414 100644
--- a/packages/babel-plugin-transform-class-properties/test/fixtures/general/foobar/expected.js
+++ b/packages/babel-plugin-transform-class-properties/test/fixtures/general/foobar/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var Child =
 /*#__PURE__*/
 function (_Parent) {
diff --git a/packages/babel-plugin-transform-class-properties/test/fixtures/loose/foobar/expected.js b/packages/babel-plugin-transform-class-properties/test/fixtures/loose/foobar/expected.js
index cf6a9bc02c..f43f546b7c 100644
--- a/packages/babel-plugin-transform-class-properties/test/fixtures/loose/foobar/expected.js
+++ b/packages/babel-plugin-transform-class-properties/test/fixtures/loose/foobar/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var Child =
 /*#__PURE__*/
 function (_Parent) {
diff --git a/packages/babel-plugin-transform-class-properties/test/fixtures/regression/6154/expected.js b/packages/babel-plugin-transform-class-properties/test/fixtures/regression/6154/expected.js
index 01805e5c56..c027b23cbc 100644
--- a/packages/babel-plugin-transform-class-properties/test/fixtures/regression/6154/expected.js
+++ b/packages/babel-plugin-transform-class-properties/test/fixtures/regression/6154/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 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 _instanceof(left, right) { if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) { return right[Symbol.hasInstance](left); } else { return left instanceof right; } }
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/5817/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/5817/expected.js
index 2fe6ea970f..0abfa635e3 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/5817/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/5817/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var A =
 /*#__PURE__*/
 function (_B) {
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2494/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2494/expected.js
index 86a3c654b2..7ee2040344 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2494/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2494/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var x = {
   Foo:
   /*#__PURE__*/
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2997/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2997/expected.js
index b46893d0e6..8ecfecbaaa 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2997/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T2997/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var A = function A() {
   babelHelpers.classCallCheck(this, A);
 };
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6712/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6712/expected.js
index 96e00e6922..08cac4b578 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6712/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6712/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var A =
 /*#__PURE__*/
 function () {
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 b5fa2e3253..6b2fd1e691 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
@@ -1,5 +1,3 @@
-"use strict";
-
 var Example =
 /*#__PURE__*/
 function () {
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7010/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7010/expected.js
index 3d7a460b5a..4f8dfbdae2 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7010/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7010/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var Foo =
 /*#__PURE__*/
 function () {
diff --git a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7537/expected.js b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7537/expected.js
index ae764cf723..1a7251e480 100644
--- a/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7537/expected.js
+++ b/packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T7537/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 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; }
diff --git a/packages/babel-plugin-transform-es2015-modules-amd/src/index.js b/packages/babel-plugin-transform-es2015-modules-amd/src/index.js
index 4c2fce1bf6..b549ac4204 100644
--- a/packages/babel-plugin-transform-es2015-modules-amd/src/index.js
+++ b/packages/babel-plugin-transform-es2015-modules-amd/src/index.js
@@ -1,5 +1,6 @@
 import template from "babel-template";
 import {
+  isModule,
   rewriteModuleStatementsAndPrepareHeader,
   hasExports,
   isSideEffectImport,
@@ -18,6 +19,8 @@ export default function({ types: t }) {
     visitor: {
       Program: {
         exit(path, state) {
+          if (!isModule(path)) return;
+
           const {
             loose,
             allowTopLevelThis,
diff --git a/packages/babel-plugin-transform-es2015-modules-commonjs/src/index.js b/packages/babel-plugin-transform-es2015-modules-commonjs/src/index.js
index b52cfd0d1e..b7119c8774 100644
--- a/packages/babel-plugin-transform-es2015-modules-commonjs/src/index.js
+++ b/packages/babel-plugin-transform-es2015-modules-commonjs/src/index.js
@@ -1,4 +1,5 @@
 import {
+  isModule,
   rewriteModuleStatementsAndPrepareHeader,
   isSideEffectImport,
   buildNamespaceInitStatements,
@@ -11,6 +12,10 @@ export default function({ types: t }) {
     visitor: {
       Program: {
         exit(path, state) {
+          // For now this requires unambiguous rather that just sourceType
+          // because Babel currently parses all files as sourceType:module.
+          if (!isModule(path, true /* requireUnambiguous */)) return;
+
           const {
             loose,
             allowTopLevelThis,
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-arrow-function/actual.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-arrow-function/actual.mjs
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-arrow-function/actual.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-arrow-function/actual.mjs
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-arrow-function/expected.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-arrow-function/expected.js
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-arrow-function/expected.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-arrow-function/expected.js
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-call/actual.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-call/actual.mjs
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-call/actual.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-call/actual.mjs
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-call/expected.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-call/expected.js
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-call/expected.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-call/expected.js
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-declaration/actual.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-declaration/actual.mjs
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-declaration/actual.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-declaration/actual.mjs
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-declaration/expected.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-declaration/expected.js
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-declaration/expected.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-declaration/expected.js
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-reference/actual.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-reference/actual.mjs
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-reference/actual.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-reference/actual.mjs
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-reference/expected.js b/packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-reference/expected.js
similarity index 100%
rename from packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/undefined-this-root-reference/expected.js
rename to packages/babel-plugin-transform-es2015-modules-commonjs/test/fixtures/misc/undefined-this-root-reference/expected.js
diff --git a/packages/babel-plugin-transform-es2015-modules-umd/src/index.js b/packages/babel-plugin-transform-es2015-modules-umd/src/index.js
index 1cf4fa9f05..c984cb53e7 100644
--- a/packages/babel-plugin-transform-es2015-modules-umd/src/index.js
+++ b/packages/babel-plugin-transform-es2015-modules-umd/src/index.js
@@ -1,6 +1,7 @@
 import { basename, extname } from "path";
 import template from "babel-template";
 import {
+  isModule,
   rewriteModuleStatementsAndPrepareHeader,
   hasExports,
   isSideEffectImport,
@@ -107,6 +108,8 @@ export default function({ types: t }) {
     visitor: {
       Program: {
         exit(path, state) {
+          if (!isModule(path)) return;
+
           const {
             globals,
             exactGlobals,
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 16ca53f948..d39c634e40 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
@@ -1,5 +1,3 @@
-"use strict";
-
 // @flow
 var C =
 /*#__PURE__*/
diff --git a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-return-type-annotation/expected.js b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-return-type-annotation/expected.js
index 68d6c4494b..cca8f738c3 100644
--- a/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-return-type-annotation/expected.js
+++ b/packages/babel-plugin-transform-flow-comments/test/fixtures/flow-comments/transformed-class-method-return-type-annotation/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 // @flow
 var C =
 /*#__PURE__*/
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 42a2b16879..f5f9fc21cb 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
@@ -1,5 +1,3 @@
-"use strict";
-
 var C =
 /*#__PURE__*/
 function () {
diff --git a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-return-type-annotation/expected.js b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-return-type-annotation/expected.js
index 8613c02f7e..8665e0ced3 100644
--- a/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-return-type-annotation/expected.js
+++ b/packages/babel-plugin-transform-flow-strip-types/test/fixtures/regression/transformed-class-method-return-type-annotation/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var C =
 /*#__PURE__*/
 function () {
diff --git a/packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/expected.js b/packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/expected.js
index ffaa4b9a4e..babd815f2d 100644
--- a/packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/expected.js
+++ b/packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 function test(fn) {
   return function _callee() {
     var _args = arguments;
diff --git a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/options.json b/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/options.json
index 51bfaafbee..95296e5e98 100644
--- a/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/options.json
+++ b/packages/babel-plugin-transform-strict-mode/test/fixtures/strict-mode/options.json
@@ -1,3 +1,3 @@
 {
-  "plugins": ["transform-strict-mode", "transform-es2015-modules-commonjs"]
+  "plugins": ["transform-strict-mode"]
 }
diff --git a/packages/babel-preset-es2015/test/fixtures/preset-options/spec/expected.js b/packages/babel-preset-es2015/test/fixtures/preset-options/spec/expected.js
index e4b0c4adb6..889d4b054a 100644
--- a/packages/babel-preset-es2015/test/fixtures/preset-options/spec/expected.js
+++ b/packages/babel-preset-es2015/test/fixtures/preset-options/spec/expected.js
@@ -1,11 +1,9 @@
-"use strict";
-
-var _this = void 0;
+var _this = this;
 
 "1".concat(a);
 (function () {
   babelHelpers.newArrowCheck(this, _this);
-}).bind(void 0);
+}).bind(this);
 
 function a() {
   var _this2 = this;
diff --git a/packages/babel-runtime/scripts/build-dist.js b/packages/babel-runtime/scripts/build-dist.js
index 4f9a3c5a1f..f581bdb4a3 100644
--- a/packages/babel-runtime/scripts/build-dist.js
+++ b/packages/babel-runtime/scripts/build-dist.js
@@ -104,7 +104,7 @@ function buildRuntimeRewritePlugin(relativePath, helperName) {
 }
 
 function buildHelper(helperName, modules, useBuiltIns) {
-  const tree = t.program(helpers.get(helperName).nodes);
+  const tree = t.program(helpers.get(helperName).nodes, [], "module");
 
   const transformOpts = makeTransformOpts(modules, useBuiltIns);
 
diff --git a/packages/babel-standalone/test/babel.js b/packages/babel-standalone/test/babel.js
index 73d7802727..088a78408d 100644
--- a/packages/babel-standalone/test/babel.js
+++ b/packages/babel-standalone/test/babel.js
@@ -18,7 +18,7 @@ describe("babel-standalone", () => {
     const output = Babel.transform("class A {}", {
       presets: ["es2015-loose"],
     }).code;
-    assert.equal(output, '"use strict";\n\nvar A = function A() {};');
+    assert.equal(output, "var A = function A() {};");
   });
   it("handles the typescript preset", () => {
     const output = Babel.transform("var a: string;", {
@@ -56,7 +56,7 @@ describe("babel-standalone", () => {
     };
     const output = Babel.transformFromAst(ast, "42", { presets: ["es2015"] })
       .code;
-    assert.equal(output, '"use strict";\n' + "\n" + "42;");
+    assert.equal(output, "42;");
   });
 
   it("handles the react preset", () => {
diff --git a/packages/babel-types/src/definitions/core.js b/packages/babel-types/src/definitions/core.js
index abdcd57bb1..9bb1181762 100644
--- a/packages/babel-types/src/definitions/core.js
+++ b/packages/babel-types/src/definitions/core.js
@@ -513,13 +513,14 @@ defineType("NewExpression", { inherits: "CallExpression" });
 
 defineType("Program", {
   visitor: ["directives", "body"],
-  builder: ["body", "directives"],
+  builder: ["body", "directives", "sourceType"],
   fields: {
     sourceFile: {
       validate: assertValueType("string"),
     },
     sourceType: {
       validate: assertOneOf("script", "module"),
+      default: "script",
     },
     directives: {
       validate: chain(