diff --git a/extensions/discord/src/channel.test.ts b/extensions/discord/src/channel.test.ts
index 898cea6a045e..434191cd68d3 100644
--- a/extensions/discord/src/channel.test.ts
+++ b/extensions/discord/src/channel.test.ts
@@ -110,7 +110,11 @@ function objectArgAt(
 }
 
 function argAt(mock: MockWithCalls, callIndex: number, argIndex: number): unknown {
-  return mock.mock.calls[callIndex]?.[argIndex];
+  const call = mock.mock.calls[callIndex];
+  if (!call || !(argIndex in call)) {
+    throw new Error(`expected call ${callIndex} argument ${argIndex}`);
+  }
+  return call[argIndex];
 }
 
 function recordField(value: unknown, field: string): Record<string, unknown> {
@@ -444,7 +448,7 @@ describe("discordPlugin outbound", () => {
         target: "channel:222",
       });
 
-      expect(fetchPermissionsSpy.mock.calls[0]?.[0]).toBe("222");
+      expect(argAt(fetchPermissionsSpy, 0, 0)).toBe("222");
       expect(objectArgAt(fetchPermissionsSpy, 0, 1).token).toBe("discord-token");
       const permissions = recordField(diagnostics?.details?.permissions, "permissions");
       expect(permissions.channelId).toBe("222");
diff --git a/extensions/discord/src/voice-message.test.ts b/extensions/discord/src/voice-message.test.ts
index 2a753efc5865..e53cf89a23ac 100644
--- a/extensions/discord/src/voice-message.test.ts
+++ b/extensions/discord/src/voice-message.test.ts
@@ -63,7 +63,11 @@ describe("ensureOggOpus", () => {
   }
 
   function readSingleCommandArgs(mock: typeof runFfprobeMock | typeof runFfmpegMock): string[] {
-    const args = mock.mock.calls[0]?.[0];
+    const [call] = mock.mock.calls;
+    if (!call) {
+      throw new Error("missing command call");
+    }
+    const [args] = call;
     if (!Array.isArray(args) || !args.every((arg): arg is string => typeof arg === "string")) {
       throw new Error("missing command args");
     }