diff --git a/react-for-template/src/TemplateMapViewController.ts b/react-for-template/src/TemplateMapViewController.ts
index 6009e9d..fcbce32 100644
--- a/react-for-template/src/TemplateMapViewController.ts
+++ b/react-for-template/src/TemplateMapViewController.ts
@@ -193,12 +193,14 @@ export class TemplateMapViewController extends BaseMapViewController implements
     }
 
     async clearOverlays(): Promise<void> {
-        await this.markerController.clear();
-        await this.circleController.clear();
-        await this.polylineController.clear();
-        await this.polygonController.clear();
-        await this.groundImageController.clear();
-        await this.rasterLayerController.clear();
+        await this.clearOverlayControllers([
+          this.markerController,
+          this.circleController,
+          this.polylineController,
+          this.polygonController,
+          this.groundImageController,
+          this.rasterLayerController,
+        ]);
     }
 
     /** 地図の破棄。登録済みコントローラの後始末はコアがやる。 */
diff --git a/react-for-template/test/TemplateDriverConformance.test.mjs b/react-for-template/test/TemplateDriverConformance.test.mjs
index 7aa7abe..a17105f 100644
--- a/react-for-template/test/TemplateDriverConformance.test.mjs
+++ b/react-for-template/test/TemplateDriverConformance.test.mjs
@@ -33,6 +33,16 @@ test('every overlay kind is reachable from the Capable facade and the cascade',
     MapDriverConformance.checkOverlaySlots(controller.overlayControllers);
 });
 
+/**
+ * `clearOverlays()` は自分の 6 つだけでなく、拡張が登録したマーカーのコントローラ
+ * （クラスタリングの `StrategyMarkerController` など）も clear すること。
+ * `clearOverlayControllers()` を通さないと、ここで落ちる。
+ */
+test('clearOverlays() reaches the marker controllers extensions register', async () => {
+    const controller = new TemplateMapViewController(new TemplateMap());
+    await MapDriverConformance.checkClearOverlaysReachesExtensions(controller);
+});
+
 test('zoom converter round-trips, is monotonic and clamps', () => {
     const controller = new TemplateMapViewController(new TemplateMap());
     MapDriverConformance.checkZoomConverter(controller.zoomConverter);