diff --git a/packages/playwright-core/src/server/chromium/crBrowser.ts b/packages/playwright-core/src/server/chromium/crBrowser.ts
index 37c4d7110d..8eb1e35928 100644
--- a/packages/playwright-core/src/server/chromium/crBrowser.ts
+++ b/packages/playwright-core/src/server/chromium/crBrowser.ts
@@ -243,7 +243,12 @@ export class CRBrowser extends Browser {
 
   _onDownloadWillBegin(payload: Protocol.Browser.downloadWillBeginPayload) {
     const page = this._findOwningPage(payload.frameId);
-    assert(page, 'Download started in unknown page: ' + JSON.stringify(payload));
+    if (!page) {
+      // There might be no page when download originates from something unusual, like
+      // a DevTools window or maybe an extension page.
+      // See https://github.com/microsoft/playwright/issues/22551.
+      return;
+    }
     page.willBeginDownload();
 
     let originPage = page._initializedPage;
diff --git a/packages/playwright-core/src/server/firefox/ffBrowser.ts b/packages/playwright-core/src/server/firefox/ffBrowser.ts
index 52bc17c1cc..7cd57188ef 100644
--- a/packages/playwright-core/src/server/firefox/ffBrowser.ts
+++ b/packages/playwright-core/src/server/firefox/ffBrowser.ts
@@ -118,8 +118,7 @@ export class FFBrowser extends Browser {
   }
 
   _onDownloadCreated(payload: Protocol.Browser.downloadCreatedPayload) {
-    const ffPage = this._ffPages.get(payload.pageTargetId)!;
-    assert(ffPage);
+    const ffPage = this._ffPages.get(payload.pageTargetId);
     if (!ffPage)
       return;