diff --git a/extensions/signal/src/monitor.tool-result.sends-tool-summaries-responseprefix.test.ts b/extensions/signal/src/monitor.tool-result.sends-tool-summaries-responseprefix.test.ts
index faab0f9a78f..8087b0e5342 100644
--- a/extensions/signal/src/monitor.tool-result.sends-tool-summaries-responseprefix.test.ts
+++ b/extensions/signal/src/monitor.tool-result.sends-tool-summaries-responseprefix.test.ts
@@ -140,7 +140,7 @@ describe("monitorSignalProvider tool results", () => {
     await vi.waitFor(() => {
       expect(sendMock).toHaveBeenCalledTimes(1);
     });
-    expect(sendMock.mock.calls.at(0)?.[1]).toBe("PFX final reply");
+    expect(sendMock.mock.calls[0]?.[1]).toBe("PFX final reply");
   });
 
   it("replies with pairing code when dmPolicy is pairing and no allowFrom is set", async () => {
@@ -165,7 +165,7 @@ describe("monitorSignalProvider tool results", () => {
     expect(replyMock).not.toHaveBeenCalled();
     expect(upsertPairingRequestMock).toHaveBeenCalled();
     expect(sendMock).toHaveBeenCalledTimes(1);
-    expectPairingReplyText(String(sendMock.mock.calls.at(0)?.[1] ?? ""), {
+    expectPairingReplyText(String(sendMock.mock.calls[0]?.[1] ?? ""), {
       channel: "signal",
       idLine: "Your Signal number: +15550001111",
       code: "PAIRCODE",