diff --git a/node/src/server.ts b/node/src/server.ts
index 15cc318..a58605d 100644
--- a/node/src/server.ts
+++ b/node/src/server.ts
@@ -156,10 +156,11 @@ export async function startServer(
 ): Promise<{ app: FastifyInstance; store: MailboxStore; sweepTimer: NodeJS.Timeout | null }> {
   const store = new MailboxStore(cfg.dbPath);
   const app = await buildServer(cfg, store);
-  await app.listen({ host: cfg.bind, port: cfg.port });
-  const sweepTimer = startSweep(store, cfg, app.log);
+  const timerRef: { current: NodeJS.Timeout | null } = { current: null };
   app.addHook("onClose", async () => {
-    if (sweepTimer) clearInterval(sweepTimer);
+    if (timerRef.current) clearInterval(timerRef.current);
   });
-  return { app, store, sweepTimer };
+  await app.listen({ host: cfg.bind, port: cfg.port });
+  timerRef.current = startSweep(store, cfg, app.log);
+  return { app, store, sweepTimer: timerRef.current };
 }