diff --git a/lib/src/showcase_widget.dart b/lib/src/showcase_widget.dart
index 8e800497..72fb5202 100644
--- a/lib/src/showcase_widget.dart
+++ b/lib/src/showcase_widget.dart
@@ -124,7 +124,7 @@ class ShowCaseWidgetState extends State<ShowCaseWidget> {
   int? activeWidgetId;
   RenderBox? rootRenderObject;
   Size? rootWidgetSize;
-  Key anchoredOverlayKey = UniqueKey();
+  final Key anchoredOverlayKey = UniqueKey();
 
   /// These properties are only here so that it can be accessed by
   /// [Showcase]