diff --git a/apps/comments/src/comments-activity-tab.ts b/apps/comments/src/comments-activity-tab.ts
index b738242cf574c..44ec58972c0d9 100644
--- a/apps/comments/src/comments-activity-tab.ts
+++ b/apps/comments/src/comments-activity-tab.ts
@@ -15,7 +15,7 @@ import { getComments } from './services/GetComments.ts'
  * Register the comments plugins for the Activity sidebar
  */
 export function registerCommentsPlugins() {
-	let app: App
+	let app: App | undefined
 
 	window.OCA.Activity.registerSidebarAction({
 		mount: async (el: HTMLElement, { node, reload }: { node: INode, reload: () => void }) => {
@@ -38,6 +38,7 @@ export function registerCommentsPlugins() {
 		unmount: () => {
 			// destroy previous instance if available
 			app?.unmount()
+			app = undefined
 		},
 	})