diff --git a/packages/flutter/lib/src/widgets/scrollbar.dart b/packages/flutter/lib/src/widgets/scrollbar.dart
index bb63d5561d..c0cf60055c 100644
--- a/packages/flutter/lib/src/widgets/scrollbar.dart
+++ b/packages/flutter/lib/src/widgets/scrollbar.dart
@@ -1320,7 +1320,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   ScrollController? _cachedController;
   Timer? _fadeoutTimer;
   late AnimationController _fadeoutAnimationController;
-  late Animation<double> _fadeoutOpacityAnimation;
+  late CurvedAnimation _fadeoutOpacityAnimation;
   final GlobalKey  _scrollbarPainterKey = GlobalKey();
   bool _hoverIsActive = false;
   bool _thumbDragging = false;
@@ -2006,6 +2006,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
     _fadeoutAnimationController.dispose();
     _fadeoutTimer?.cancel();
     scrollbarPainter.dispose();
+    _fadeoutOpacityAnimation.dispose();
     super.dispose();
   }
 
diff --git a/packages/flutter/test/rendering/viewport_test.dart b/packages/flutter/test/rendering/viewport_test.dart
index 18c830bb6e..83a3862568 100644
--- a/packages/flutter/test/rendering/viewport_test.dart
+++ b/packages/flutter/test/rendering/viewport_test.dart
@@ -14,6 +14,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 class _TestSliverPersistentHeaderDelegate extends SliverPersistentHeaderDelegate {
   _TestSliverPersistentHeaderDelegate({
@@ -2054,7 +2055,10 @@ void main() {
       expect(tester.getTopLeft(find.text('Item 9')).dy, 226.0);
     });
 
-    testWidgets('allows overscrolling on default platforms - vertical', (WidgetTester tester) async {
+    testWidgets('allows overscrolling on default platforms - vertical',
+    // TODO(polina-c): remove when fixed https://github.com/flutter/flutter/issues/145600 [leak-tracking-opt-in]
+    experimentalLeakTesting: LeakTesting.settings.withTracked(classes: const <String>['CurvedAnimation']),
+    (WidgetTester tester) async {
       // Regression test for https://github.com/flutter/flutter/issues/10949
       // Scrollables should overscroll by default on iOS and macOS
       final  ScrollController controller = ScrollController();