diff --git a/extensions/microsoft-foundry/index.test.ts b/extensions/microsoft-foundry/index.test.ts
index 4bae7310172..5f40df1fb6a 100644
--- a/extensions/microsoft-foundry/index.test.ts
+++ b/extensions/microsoft-foundry/index.test.ts
@@ -53,7 +53,7 @@ function registerProvider() {
     }),
   );
   expect(registerProviderMock).toHaveBeenCalledTimes(1);
-  const firstCall = registerProviderMock.mock.calls.at(0);
+  const firstCall = registerProviderMock.mock.calls[0];
   if (!firstCall) {
     throw new Error("expected Microsoft Foundry provider registration");
   }