diff --git a/src/media/fetch.ts b/src/media/fetch.ts
index 55d15a63d..367a8b7bc 100644
--- a/src/media/fetch.ts
+++ b/src/media/fetch.ts
@@ -8,9 +8,14 @@ type FetchMediaResult = {
   fileName?: string;
 };
 
+export type FetchLike = (
+  input: RequestInfo | URL,
+  init?: RequestInit,
+) => Promise<Response>;
+
 type FetchMediaOptions = {
   url: string;
-  fetchImpl?: typeof fetch;
+  fetchImpl?: FetchLike;
   filePathHint?: string;
 };
 
@@ -57,7 +62,7 @@ export async function fetchRemoteMedia(
   options: FetchMediaOptions,
 ): Promise<FetchMediaResult> {
   const { url, fetchImpl, filePathHint } = options;
-  const fetcher = fetchImpl ?? globalThis.fetch;
+  const fetcher: FetchLike | undefined = fetchImpl ?? globalThis.fetch;
   if (!fetcher) {
     throw new Error("fetch is not available");
   }
diff --git a/src/slack/monitor.ts b/src/slack/monitor.ts
index 62278e899..11a8a17ce 100644
--- a/src/slack/monitor.ts
+++ b/src/slack/monitor.ts
@@ -45,7 +45,7 @@ import {
 import { danger, logVerbose, shouldLogVerbose } from "../globals.js";
 import { enqueueSystemEvent } from "../infra/system-events.js";
 import { getChildLogger } from "../logging.js";
-import { fetchRemoteMedia } from "../media/fetch.js";
+import { fetchRemoteMedia, type FetchLike } from "../media/fetch.js";
 import { saveMediaBuffer } from "../media/store.js";
 import { buildPairingReply } from "../pairing/pairing-messages.js";
 import {
@@ -355,7 +355,7 @@ async function resolveSlackMedia(params: {
     const url = file.url_private_download ?? file.url_private;
     if (!url) continue;
     try {
-      const fetchImpl: typeof fetch = (input, init) => {
+      const fetchImpl: FetchLike = (input, init) => {
         const headers = new Headers(init?.headers);
         headers.set("Authorization", `Bearer ${params.token}`);
         return fetch(input, { ...init, headers });