diff --git a/samples-dev/swarm/swarm_ui_lib/touch/TouchUtil.dart b/samples-dev/swarm/swarm_ui_lib/touch/TouchUtil.dart
index 0a841b753b2..dc12c0e1f70 100644
--- a/samples-dev/swarm/swarm_ui_lib/touch/TouchUtil.dart
+++ b/samples-dev/swarm/swarm_ui_lib/touch/TouchUtil.dart
@@ -359,4 +359,12 @@ class MockTouchEvent implements TouchEvent {
   /*InputDevice*/ get sourceDevice {
     throw new UnimplementedError();
   }
+
+  bool get composed {
+    throw new UnimplementedError();
+  }
+
+  List<EventTarget> composedPath() {
+    throw new UnimplementedError();
+  }
 }