diff --git a/src/background/handlers/attach-window-to-request.test.ts b/src/background/handlers/attach-window-to-request.test.ts
index fed077951..b458dae6e 100644
--- a/src/background/handlers/attach-window-to-request.test.ts
+++ b/src/background/handlers/attach-window-to-request.test.ts
@@ -99,6 +99,20 @@ describe('a window that is not ours must not own a request', () => {
     expect(cancelMock).not.toHaveBeenCalled();
   });
 
+  it('does not undo the attach when the tab is still at about:blank', async () => {
+    // Firefox has no `pendingUrl` and reports a freshly created window's tab
+    // as `about:blank` until the navigation commits, so on a cold open there
+    // the probe lands on exactly this shape (WALLET-1439). Repairing on it
+    // cancelled the request whose window was on screen.
+    getMock.mockResolvedValue({ id: 7, tabs: [{ url: 'about:blank' }] });
+    const { store } = makeStore();
+
+    attachWindowToRequest(store, 'r1', 7);
+    await flush();
+
+    expect(cancelMock).not.toHaveBeenCalled();
+  });
+
   it('warns when our window carries no requestId at all', async () => {
     // Without this the ownership check establishes "one of our windows" and
     // says nothing about "the window showing THIS request" — and the two are
diff --git a/src/background/handlers/attach-window-to-request.ts b/src/background/handlers/attach-window-to-request.ts
index 4c71028d7..6c716e531 100644
--- a/src/background/handlers/attach-window-to-request.ts
+++ b/src/background/handlers/attach-window-to-request.ts
@@ -67,7 +67,11 @@ export function attachWindowToRequest(
       const tab = browserWindow.tabs?.[0];
       const tabUrl = tab?.url ?? tab?.pendingUrl;
 
-      if (tabUrl == null || tabUrl === '') {
+      // Every not-yet-settled shape, per browser: Chrome reports a navigating
+      // tab as `url: ''` (the target in `pendingUrl`); Firefox has no
+      // `pendingUrl` and reports `about:blank` until the navigation commits,
+      // which is what a freshly created window's tab shows when probed.
+      if (tabUrl == null || tabUrl === '' || tabUrl === 'about:blank') {
         return;
       }