diff --git a/extensions/gradium/tts.test.ts b/extensions/gradium/tts.test.ts
index 96648d8a994..847ade1e0fa 100644
--- a/extensions/gradium/tts.test.ts
+++ b/extensions/gradium/tts.test.ts
@@ -119,7 +119,7 @@ describe("gradium tts diagnostics", () => {
     });
 
     expect(fetchMock).toHaveBeenCalledOnce();
-    const [url, init] = fetchMock.mock.calls.at(0) as [string, RequestInit];
+    const [url, init] = fetchMock.mock.calls[0] as [string, RequestInit];
     expect(url).toBe("https://api.gradium.ai/api/post/speech/tts");
     expect(init.method).toBe("POST");
     const headers = new Headers(init.headers);