diff --git a/src/gateway/server-methods/tools-catalog.test.ts b/src/gateway/server-methods/tools-catalog.test.ts
index 6f1eee9972f..802d38a1915 100644
--- a/src/gateway/server-methods/tools-catalog.test.ts
+++ b/src/gateway/server-methods/tools-catalog.test.ts
@@ -54,7 +54,7 @@ function createInvokeParams(params: Record<string, unknown>) {
 }
 
 function firstMockArg(mock: { mock: { calls: unknown[][] } }, label: string): unknown {
-  const arg = mock.mock.calls.at(0)?.at(0);
+  const arg = mock.mock.calls[0]?.[0];
   if (arg === undefined) {
     throw new Error(`Expected ${label}`);
   }
@@ -62,7 +62,7 @@ function firstMockArg(mock: { mock: { calls: unknown[][] } }, label: string): un
 }
 
 function respondCall(respond: ReturnType<typeof vi.fn>): RespondCall {
-  const call = respond.mock.calls.at(0) as RespondCall | undefined;
+  const call = respond.mock.calls[0] as RespondCall | undefined;
   if (!call) {
     throw new Error("expected respond call");
   }