diff --git a/src/client/web/src/common/env.ts b/src/client/web/src/common/env.ts
index e3804ca..732a50b 100644
--- a/src/client/web/src/common/env.ts
+++ b/src/client/web/src/common/env.ts
@@ -7,10 +7,10 @@ export function alertMsg(msg: string) {
 }
 
 export function confirmMsg(msg: string): boolean {
-  try {
+  if (confirm != null) {
     return confirm(msg);
-  } catch (e) {
-    console.log(`${msg}: yes (confirm is not implemented)`);
+  } else {
+    console.warn(`${msg}: return yes (confirm is not implemented)`);
     return true;
   }
 }
diff --git a/src/client/web/src/components/__test__/topbar.test.tsx b/src/client/web/src/components/__test__/topbar.test.tsx
index d3124c5..765e51f 100644
--- a/src/client/web/src/components/__test__/topbar.test.tsx
+++ b/src/client/web/src/components/__test__/topbar.test.tsx
@@ -16,6 +16,9 @@ import { UploadEntry, UploadState } from "../../worker/interface";
 
 
 describe("TopBar", () => {
+  // stub confirm
+  window.confirm = (message?: string): boolean => {return true;};
+
   test("logout as visitor without sharing", async () => {
     const mockWorkerClass = mock(MockWorker);
     const mockWorker = instance(mockWorkerClass);