diff --git a/pkg/js_runtime/lib/shared/async_await_error_codes.dart b/pkg/js_runtime/lib/shared/async_await_error_codes.dart
index f87406b31b0..17082302409 100644
--- a/pkg/js_runtime/lib/shared/async_await_error_codes.dart
+++ b/pkg/js_runtime/lib/shared/async_await_error_codes.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.12
+
 /// Contains error codes that transformed async/async* functions use to
 /// communicate with js_helper functions.
 
diff --git a/pkg/js_runtime/lib/shared/embedded_names.dart b/pkg/js_runtime/lib/shared/embedded_names.dart
index e2dd66d60d4..6d6de2d2fb0 100644
--- a/pkg/js_runtime/lib/shared/embedded_names.dart
+++ b/pkg/js_runtime/lib/shared/embedded_names.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.12
+
 /// Contains the names of globals that are embedded into the output by the
 /// compiler.
 ///
diff --git a/pkg/js_runtime/lib/shared/recipe_syntax.dart b/pkg/js_runtime/lib/shared/recipe_syntax.dart
index c1838614fa6..73054919a2b 100644
--- a/pkg/js_runtime/lib/shared/recipe_syntax.dart
+++ b/pkg/js_runtime/lib/shared/recipe_syntax.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.12
+
 /// Constants and predicates used for encoding and decoding type recipes.
 ///
 /// This library is shared between the compiler and the runtime system.
diff --git a/sdk/lib/_internal/js_runtime/lib/shared/async_await_error_codes.dart b/sdk/lib/_internal/js_runtime/lib/shared/async_await_error_codes.dart
index f87406b31b0..17082302409 100644
--- a/sdk/lib/_internal/js_runtime/lib/shared/async_await_error_codes.dart
+++ b/sdk/lib/_internal/js_runtime/lib/shared/async_await_error_codes.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.12
+
 /// Contains error codes that transformed async/async* functions use to
 /// communicate with js_helper functions.
 
diff --git a/sdk/lib/_internal/js_runtime/lib/shared/embedded_names.dart b/sdk/lib/_internal/js_runtime/lib/shared/embedded_names.dart
index e2dd66d60d4..6d6de2d2fb0 100644
--- a/sdk/lib/_internal/js_runtime/lib/shared/embedded_names.dart
+++ b/sdk/lib/_internal/js_runtime/lib/shared/embedded_names.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.12
+
 /// Contains the names of globals that are embedded into the output by the
 /// compiler.
 ///
diff --git a/sdk/lib/_internal/js_runtime/lib/shared/recipe_syntax.dart b/sdk/lib/_internal/js_runtime/lib/shared/recipe_syntax.dart
index c1838614fa6..73054919a2b 100644
--- a/sdk/lib/_internal/js_runtime/lib/shared/recipe_syntax.dart
+++ b/sdk/lib/_internal/js_runtime/lib/shared/recipe_syntax.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.12
+
 /// Constants and predicates used for encoding and decoding type recipes.
 ///
 /// This library is shared between the compiler and the runtime system.