diff --git a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
index 95f1f73ff4..48564666bf 100644
--- a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
+++ b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
@@ -81,12 +81,16 @@ export async function showTraceViewer(traceUrls: string[], browserName: string,
   if (traceViewerBrowser === 'chromium')
     await installAppIcon(page);
 
-  if (isUnderTest())
-    page.on('close', () => context.close(serverSideCallMetadata()).catch(() => {}));
-  else
-    page.on('close', () => process.exit());
 
-  const searchQuery = traceUrls.length ? '?' + traceUrls.map(t => `trace=${t}`).join('&') : '';
+  const params = traceUrls.map(t => `trace=${t}`);
+  if (isUnderTest()) {
+    params.push('isUnderTest=true');
+    page.on('close', () => context.close(serverSideCallMetadata()).catch(() => {}));
+  } else {
+    page.on('close', () => process.exit());
+  }
+
+  const searchQuery = params.length ? '?' + params.join('&') : '';
   await page.mainFrame().goto(serverSideCallMetadata(), urlPrefix + `/trace/index.html${searchQuery}`);
   return context;
 }
diff --git a/packages/trace-viewer/src/index.tsx b/packages/trace-viewer/src/index.tsx
index 01f6597d72..bfec2f876b 100644
--- a/packages/trace-viewer/src/index.tsx
+++ b/packages/trace-viewer/src/index.tsx
@@ -24,7 +24,8 @@ import '@web/common.css';
 (async () => {
   applyTheme();
   if (window.location.protocol !== 'file:') {
-    await new Promise(f => setTimeout(f, 500));
+    if (window.location.href.includes('isUnderTest=true'))
+      await new Promise(f => setTimeout(f, 1000));
     navigator.serviceWorker.register('sw.bundle.js');
     if (!navigator.serviceWorker.controller) {
       await new Promise<void>(f => {