diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0dcd52bc..f3095f45 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 5.1.1 [#unreleased]
+
+- Fixed [#659](https://github.com/SimformSolutionsPvtLtd/showcaseview/issues/659) - Fix null-check crash in `ShowcaseController._initRootWidget` when the `Showcase` is unmounted in the same frame it mounts. Fixed by @[apurva-simform](https://github.com/apurva-simform)
+
 ## 5.1.0
 
 - Fixed [#650](https://github.com/SimformSolutionsPvtLtd/showcaseview/issues/650) - Fix null-check crash in ShowcaseService.getController during didUpdateWidget. Fixed by @[vatsaltanna-simformsolutions](https://github.com/vatsaltanna-simformsolutions)
diff --git a/lib/src/showcase/showcase_controller.dart b/lib/src/showcase/showcase_controller.dart
index 865e5169..42ee379f 100644
--- a/lib/src/showcase/showcase_controller.dart
+++ b/lib/src/showcase/showcase_controller.dart
@@ -274,6 +274,9 @@ class ShowcaseController {
   ///
   /// Must be called after the widget is mounted to ensure proper measurements.
   void _initRootWidget() {
+    // register()'s post-frame callback can fire after the Showcase was
+    // unmounted in the same frame, and State.context throws on a dead State.
+    if (!_mounted) return;
     final rootWidget = _context.findRootAncestorStateOfType<State<Overlay>>();
     rootRenderObject = rootWidget?.context.findRenderObject() as RenderBox?;
     rootWidgetSize = rootWidget == null