diff --git a/extensions/mattermost/src/mattermost/slash-http.test.ts b/extensions/mattermost/src/mattermost/slash-http.test.ts
index bc558a6a7c4..e98752d92f0 100644
--- a/extensions/mattermost/src/mattermost/slash-http.test.ts
+++ b/extensions/mattermost/src/mattermost/slash-http.test.ts
@@ -142,6 +142,11 @@ async function runSlashRequest(params: {
   return response;
 }
 
+function firstLogMessage(log: ReturnType<typeof vi.fn>): string {
+  const message = log.mock.calls[0]?.[0];
+  return typeof message === "string" ? message : "";
+}
+
 describe("slash-http", () => {
   beforeEach(() => {
     resetMattermostSlashCommandValidationCacheForTests();
@@ -628,7 +633,7 @@ describe("slash-http", () => {
     ).resolves.toBe(false);
 
     expect(log).toHaveBeenCalledTimes(1);
-    const message = log.mock.calls.at(0)?.[0] ?? "";
+    const message = firstLogMessage(log);
     expect(message).not.toMatch(/[\r\n\t]/u);
     expect(message).toContain("deleted command cmd-1  spoofed");
     expect(message).toContain("using team list fallback");
@@ -753,7 +758,7 @@ describe("slash-http", () => {
     ).resolves.toBe(true);
 
     expect(log).toHaveBeenCalledTimes(1);
-    const message = log.mock.calls.at(0)?.[0] ?? "";
+    const message = firstLogMessage(log);
     expect(message).not.toMatch(/[\r\n\t]/u);
     expect(message).toContain("/oc_status  spoofed");
     expect(message).toContain("primary token=[redacted]");
@@ -792,7 +797,7 @@ describe("slash-http", () => {
     ).resolves.toBe(false);
 
     expect(log).toHaveBeenCalledTimes(1);
-    const message = log.mock.calls.at(0)?.[0] ?? "";
+    const message = firstLogMessage(log);
     expect(message).not.toMatch(/[\r\n\t]/u);
     expect(message).toContain("fallback  second-line");
     expect(message).toContain("botToken: [redacted]");