diff

diff --git a/testing/scenario_app/lib/src/channel_util.dart b/testing/scenario_app/lib/src/channel_util.dart
index 24f05f2fc..5aa727218 100644
--- a/testing/scenario_app/lib/src/channel_util.dart
+++ b/testing/scenario_app/lib/src/channel_util.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
 import 'dart:convert';
 import 'dart:ui';
 
diff --git a/testing/scenario_app/lib/src/locale_initialization.dart b/testing/scenario_app/lib/src/locale_initialization.dart
index 7d9faf641..339b24c88 100644
--- a/testing/scenario_app/lib/src/locale_initialization.dart
+++ b/testing/scenario_app/lib/src/locale_initialization.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
 import 'dart:typed_data';
 import 'dart:ui';
 
diff --git a/testing/scenario_app/lib/src/send_text_focus_semantics.dart b/testing/scenario_app/lib/src/send_text_focus_semantics.dart
index 94997cf07..87f9b1701 100644
--- a/testing/scenario_app/lib/src/send_text_focus_semantics.dart
+++ b/testing/scenario_app/lib/src/send_text_focus_semantics.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
 import 'dart:typed_data';
 import 'dart:ui';
 
diff --git a/testing/scenario_app/lib/src/touches_scenario.dart b/testing/scenario_app/lib/src/touches_scenario.dart
index 6eb35eebe..47eebc07c 100644
--- a/testing/scenario_app/lib/src/touches_scenario.dart
+++ b/testing/scenario_app/lib/src/touches_scenario.dart
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.6
 import 'dart:convert';
 import 'dart:ui';