diff --git a/lib/6to5/transformation/templates/exports-module-declaration.js b/lib/6to5/transformation/templates/exports-module-declaration.js
index 32b83d4a5a..18efccea8a 100644
--- a/lib/6to5/transformation/templates/exports-module-declaration.js
+++ b/lib/6to5/transformation/templates/exports-module-declaration.js
@@ -1 +1,3 @@
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js
index e99414734f..f1973e1317 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js
@@ -14,5 +14,7 @@ define(["exports", "foo"], function (exports, _foo) {
   exports["default"] = _foo.foo;
   exports["default"] = _foo.foo;
   exports.bar = _foo.bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js
index 69e985f9d7..d66e609acb 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js
@@ -8,5 +8,7 @@ define(["exports"], function (exports) {
   exports["default"] = foo;
   exports["default"] = foo;
   exports.bar = bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js
index 156c8b1bac..7d2314001f 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js
@@ -17,5 +17,7 @@ define(["exports"], function (exports) {
     _classCallCheck(this, foo8);
   };
 
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js
index 9357e80ced..79267d3f30 100644
--- a/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js
@@ -12,5 +12,7 @@ define(["exports", "./evens"], function (exports, _evens) {
       return !isEven(n);
     };
   })(isEven);
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/overview/expected.js b/test/fixtures/transformation/es6-modules-amd/overview/expected.js
index 6970be8134..a9993c1612 100644
--- a/test/fixtures/transformation/es6-modules-amd/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/overview/expected.js
@@ -12,5 +12,7 @@ define(["exports", "foo", "foo-bar", "./directory/foo-bar"], function (exports,
   var test2 = exports.test2 = 5;
 
   exports["default"] = test;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/remap/expected.js b/test/fixtures/transformation/es6-modules-amd/remap/expected.js
index d632f7a5cd..accde1fb6e 100644
--- a/test/fixtures/transformation/es6-modules-amd/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/remap/expected.js
@@ -10,5 +10,7 @@ define(["exports"], function (exports) {
     test = 3;
     test++;
   })();
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/exports-default-non-function/expected.js b/test/fixtures/transformation/es6-modules-common/exports-default-non-function/expected.js
index a9d655e369..ac9a8a6e70 100644
--- a/test/fixtures/transformation/es6-modules-common/exports-default-non-function/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/exports-default-non-function/expected.js
@@ -3,4 +3,6 @@
 exports.Cachier = Cachier;
 exports["default"] = new Cachier();
 function Cachier(databaseName) {}
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/exports-from/expected.js b/test/fixtures/transformation/es6-modules-common/exports-from/expected.js
index 3f8dc1d7a3..8db5af8c82 100644
--- a/test/fixtures/transformation/es6-modules-common/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/exports-from/expected.js
@@ -15,4 +15,6 @@ exports.bar = _foo.foo;
 exports["default"] = _foo.foo;
 exports["default"] = _foo.foo;
 exports.bar = _foo.bar;
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/exports-named/expected.js b/test/fixtures/transformation/es6-modules-common/exports-named/expected.js
index e0b93dacb5..5930ea82df 100644
--- a/test/fixtures/transformation/es6-modules-common/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/exports-named/expected.js
@@ -7,4 +7,6 @@ exports.bar = foo;
 exports["default"] = foo;
 exports["default"] = foo;
 exports.bar = bar;
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-common/exports-variable/expected.js
index 446d62e7e6..157b333520 100644
--- a/test/fixtures/transformation/es6-modules-common/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/exports-variable/expected.js
@@ -16,4 +16,6 @@ var foo8 = exports.foo8 = function foo8() {
   _classCallCheck(this, foo8);
 };
 
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-common/hoist-function-exports/expected.js
index 355e860f52..1a175b6def 100644
--- a/test/fixtures/transformation/es6-modules-common/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/hoist-function-exports/expected.js
@@ -11,4 +11,6 @@ var isOdd = exports.isOdd = (function (isEven) {
     return !isEven(n);
   };
 })(isEven);
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/overview/expected.js b/test/fixtures/transformation/es6-modules-common/overview/expected.js
index 038e74c451..10ac16f17e 100644
--- a/test/fixtures/transformation/es6-modules-common/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/overview/expected.js
@@ -18,4 +18,6 @@ var bar = require("foo4").bar;
 var bar2 = require("foo5").foo;
 exports.test = test;
 var test = exports.test = 5;
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/remap/expected.js b/test/fixtures/transformation/es6-modules-common/remap/expected.js
index 4f3ed765f5..fb63edccd8 100644
--- a/test/fixtures/transformation/es6-modules-common/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/remap/expected.js
@@ -9,4 +9,6 @@ test = exports.test += 1;
   test = 3;
   test++;
 })();
-exports.__esModule = true;
\ No newline at end of file
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js
index 9b4c8ed6b1..84f959d5df 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js
@@ -20,5 +20,7 @@
   exports["default"] = _foo.foo;
   exports["default"] = _foo.foo;
   exports.bar = _foo.bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js
index 5c0d5970f1..3b4d067ec0 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js
@@ -14,5 +14,7 @@
   exports["default"] = foo;
   exports["default"] = foo;
   exports.bar = bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js
index 4857328e4b..e2f8a293c8 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js
@@ -23,5 +23,7 @@
     _classCallCheck(this, foo8);
   };
 
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js
index b998496e30..1241f1f68e 100644
--- a/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js
@@ -18,5 +18,7 @@
       return !isEven(n);
     };
   })(isEven);
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/overview/expected.js b/test/fixtures/transformation/es6-modules-umd/overview/expected.js
index ab37f4c843..8f0262a8ee 100644
--- a/test/fixtures/transformation/es6-modules-umd/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/overview/expected.js
@@ -18,5 +18,7 @@
   var test2 = exports.test2 = 5;
 
   exports["default"] = test;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/remap/expected.js b/test/fixtures/transformation/es6-modules-umd/remap/expected.js
index 7c177f945b..e44f8e70c5 100644
--- a/test/fixtures/transformation/es6-modules-umd/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/remap/expected.js
@@ -16,5 +16,7 @@
     test = 3;
     test++;
   })();
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });
\ No newline at end of file
diff --git a/test/fixtures/transformation/self-contained/full/expected.js b/test/fixtures/transformation/self-contained/full/expected.js
index 6e3064b562..0dc0a4d34f 100644
--- a/test/fixtures/transformation/self-contained/full/expected.js
+++ b/test/fixtures/transformation/self-contained/full/expected.js
@@ -27,4 +27,6 @@ var foo = _to5Helpers.interopRequire(_someModule);
 var bar = _to5Helpers.interopRequireWildcard(_someModule);
 
 var myWord = exports.myWord = _core.Symbol("abc");
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});