diff --git a/apps/showcase/doc/tree/selection/CheckboxDoc.vue b/apps/showcase/doc/tree/selection/CheckboxDoc.vue
index abe31e97a..f8474315c 100644
--- a/apps/showcase/doc/tree/selection/CheckboxDoc.vue
+++ b/apps/showcase/doc/tree/selection/CheckboxDoc.vue
@@ -38,7 +38,8 @@ import { NodeService } from '@/service/NodeService';
 export default {
     data() {
         return {
-            nodes: null
+            nodes: null,
+            selectedKey: null,
         };
     },
     mounted() {