diff --git a/packages/playwright-core/src/server/webkit/wkPage.ts b/packages/playwright-core/src/server/webkit/wkPage.ts
index c4cf4059b8..74fea4617f 100644
--- a/packages/playwright-core/src/server/webkit/wkPage.ts
+++ b/packages/playwright-core/src/server/webkit/wkPage.ts
@@ -785,6 +785,8 @@ export class WKPage implements PageDelegate {
       scripts.push('delete window.ondevicemotion');
       scripts.push('delete window.ondeviceorientation');
     }
+    scripts.push('if (!window.safari) window.safari = {};');
+
     for (const binding of this._page.allBindings())
       scripts.push(binding.source);
     scripts.push(...this._browserContext.initScripts);
diff --git a/tests/library/capabilities.spec.ts b/tests/library/capabilities.spec.ts
index 4644155417..5b7fc9b394 100644
--- a/tests/library/capabilities.spec.ts
+++ b/tests/library/capabilities.spec.ts
@@ -200,3 +200,11 @@ it('serviceWorker should intercept document request', async ({ page, server, bro
   await page.reload();
   expect(await page.textContent('body')).toBe('intercepted');
 });
+
+it('webkit should define window.safari', async ({ page, server, browserName }) => {
+  it.info().annotations.push({ type: 'issue', description: 'https://github.com/microsoft/playwright/issues/21037' });
+  it.skip(browserName !== 'webkit');
+  await page.goto(server.EMPTY_PAGE);
+  const defined = await page.evaluate(() => !!(window as any).safari);
+  expect(defined).toBeTruthy();
+});