diff --git a/src/media/host.ts b/src/media/host.ts
index 42f105d9c..28a45c086 100644
--- a/src/media/host.ts
+++ b/src/media/host.ts
@@ -42,9 +42,9 @@ export async function ensureMediaHosted(
   }
   if (needsServerStart && opts.startServer) {
     if (!mediaServer) {
-      mediaServer = await startMediaServer(port, TTL_MS, runtime);
+      mediaServer = await startMediaServer(port, TTL_MS, undefined, runtime);
       logInfo(
-        `🦞 Started temporary media host on http://localhost:${port}/media/:id (TTL ${TTL_MS / 1000}s)`,
+        `🦞 Started temporary media host on http://127.0.0.1:${port}/media/:id (TTL ${TTL_MS / 1000}s)`,
         runtime,
       );
       mediaServer.unref?.();
diff --git a/src/media/server.test.ts b/src/media/server.test.ts
index 34182c5f2..4adcc92d8 100644
--- a/src/media/server.test.ts
+++ b/src/media/server.test.ts
@@ -54,6 +54,13 @@ describe("media server", () => {
     await new Promise((r) => server.close(r));
   });
 
+  it("binds to loopback by default", async () => {
+    const server = await startMediaServer(0, 5_000);
+    const addr = server.address() as AddressInfo;
+    expect(["127.0.0.1", "::1"]).toContain(addr.address);
+    await new Promise((r) => server.close(r));
+  });
+
   it("expires old media", async () => {
     const file = path.join(MEDIA_DIR, "old");
     await fs.writeFile(file, "stale");
diff --git a/src/media/server.ts b/src/media/server.ts
index 4791352d8..1b1430e32 100644
--- a/src/media/server.ts
+++ b/src/media/server.ts
@@ -83,12 +83,13 @@ export function attachMediaRoutes(
 export async function startMediaServer(
   port: number,
   ttlMs = DEFAULT_TTL_MS,
+  host = "127.0.0.1",
   runtime: RuntimeEnv = defaultRuntime,
 ): Promise<Server> {
   const app = express();
   attachMediaRoutes(app, ttlMs, runtime);
   return await new Promise((resolve, reject) => {
-    const server = app.listen(port);
+    const server = app.listen(port, host);
     server.once("listening", () => resolve(server));
     server.once("error", (err) => {
       runtime.error(danger(`Media server failed: ${String(err)}`));