diff --git a/shell/common/fixtures/shell_test.dart b/shell/common/fixtures/shell_test.dart
index 1e87d134c75..408e53bf7a7 100644
--- a/shell/common/fixtures/shell_test.dart
+++ b/shell/common/fixtures/shell_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart=2.10
+
 import 'dart:convert' show utf8, json;
 import 'dart:isolate';
 import 'dart:typed_data';
diff --git a/shell/platform/embedder/fixtures/main.dart b/shell/platform/embedder/fixtures/main.dart
index 36fc996ee2f..81fc2e0c35b 100644
--- a/shell/platform/embedder/fixtures/main.dart
+++ b/shell/platform/embedder/fixtures/main.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart=2.10
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui';