diff --git a/framework/animation/generators.dart b/framework/animation/generators.dart
index 0c5a82bc567..e0ac5fbe425 100644
--- a/framework/animation/generators.dart
+++ b/framework/animation/generators.dart
@@ -6,6 +6,7 @@ import 'curves.dart';
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:sky' as sky;
+import 'mechanics.dart';
 
 abstract class Generator {
   Stream<double> get onTick;