diff --git a/lib/6to5/transformation/modules/system.js b/lib/6to5/transformation/modules/system.js
index b81d69a480..dccb045cfa 100644
--- a/lib/6to5/transformation/modules/system.js
+++ b/lib/6to5/transformation/modules/system.js
@@ -2,18 +2,19 @@
 
 module.exports = SystemFormatter;
 
-var AMDFormatter = require("./amd");
-var useStrict    = require("../helpers/use-strict");
-var traverse     = require("../../traverse");
-var util         = require("../../util");
-var t            = require("../../types");
-var _            = require("lodash");
+var DefaultFormatter = require("./_default");
+var AMDFormatter     = require("./amd");
+var useStrict        = require("../helpers/use-strict");
+var traverse         = require("../../traverse");
+var util             = require("../../util");
+var t                = require("../../types");
+var _                = require("lodash");
 
 function SystemFormatter(file) {
   this.exportIdentifier = file.generateUidIdentifier("export");
   this.noInteropRequire = true;
 
-  AMDFormatter.apply(this, arguments);
+  DefaultFormatter.apply(this, arguments);
 }
 
 util.inherits(SystemFormatter, AMDFormatter);
diff --git a/test/fixtures/transformation/es6-modules-system/exports-from/expected.js b/test/fixtures/transformation/es6-modules-system/exports-from/expected.js
index a0cb90f00d..b7b8242360 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-from/expected.js
@@ -21,8 +21,6 @@ System.register(["foo"], function (_export) {
 
       _export("bar", _foo.bar);
     }],
-    execute: function () {
-      exports.__esModule = true;
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/fixtures/transformation/es6-modules-system/exports-generator/expected.js b/test/fixtures/transformation/es6-modules-system/exports-generator/expected.js
index 16c9b90aaf..fd897196b1 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-generator/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-generator/expected.js
@@ -18,8 +18,6 @@ System.register([], function (_export) {
 
   return {
     setters: [],
-    execute: function () {
-      exports.__esModule = true;
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/fixtures/transformation/es6-modules-system/exports-named/expected.js b/test/fixtures/transformation/es6-modules-system/exports-named/expected.js
index e0f170a393..86487ee2f5 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-named/expected.js
@@ -17,8 +17,6 @@ System.register([], function (_export) {
       _export("default", foo);
 
       _export("bar", bar);
-
-      exports.__esModule = true;
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js
index 9483aa2386..740ae60f6c 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js
@@ -16,7 +16,6 @@ System.register([], function (_export) {
       foo6 = _export("foo6", 3);
       foo8 = _export("foo8", function foo8() {});
       _export("foo3", foo3 = 5);
-      exports.__esModule = true;
     }
   };
 });
diff --git a/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js
index a961542915..fd752cdebf 100644
--- a/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js
@@ -19,7 +19,6 @@ System.register(["./evens"], function (_export) {
           return !isEven(n);
         };
       })(isEven));
-      exports.__esModule = true;
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/fixtures/transformation/es6-modules-system/overview/expected.js b/test/fixtures/transformation/es6-modules-system/overview/expected.js
index c9b76bc1b7..538640f07d 100644
--- a/test/fixtures/transformation/es6-modules-system/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/overview/expected.js
@@ -14,8 +14,6 @@ System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
 
       test2 = _export("test2", 5);
       _export("default", test);
-
-      exports.__esModule = true;
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/fixtures/transformation/es6-modules-system/remap/expected.js b/test/fixtures/transformation/es6-modules-system/remap/expected.js
index 2281e2092e..b4d66336c9 100644
--- a/test/fixtures/transformation/es6-modules-system/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/remap/expected.js
@@ -14,7 +14,6 @@ System.register([], function (_export) {
         test = 3;
         test++;
       })();
-      exports.__esModule = true;
     }
   };
-});
\ No newline at end of file
+});