diff --git a/packages/flutter_sprites/lib/src/physics_collision_groups.dart b/packages/flutter_sprites/lib/src/physics_collision_groups.dart
index 150e5e5e60e..b40043b57c5 100644
--- a/packages/flutter_sprites/lib/src/physics_collision_groups.dart
+++ b/packages/flutter_sprites/lib/src/physics_collision_groups.dart
@@ -7,7 +7,7 @@ class _PhysicsCollisionGroups {
     getBitmaskForKeys(["Default"]);
   }
 
-  Map<Object,int> keyLookup = {};
+  Map<Object,int> keyLookup = <Object,int>{};
 
   List<Object> getKeysForBitmask(int bitmask) {
     List<Object> keys = [];