diff --git a/src/hooks/useServiceWorkerMessages.ts b/src/hooks/useServiceWorkerMessages.ts
index af5ee64..3af9061 100644
--- a/src/hooks/useServiceWorkerMessages.ts
+++ b/src/hooks/useServiceWorkerMessages.ts
@@ -2,6 +2,15 @@
 
 import { useEffect, useCallback, useRef } from 'react';
 
+// Background Sync API types (not in default TypeScript libs)
+interface SyncManager {
+  register(tag: string): Promise<void>;
+}
+
+interface ServiceWorkerRegistrationWithSync extends ServiceWorkerRegistration {
+  sync: SyncManager;
+}
+
 interface UseServiceWorkerMessagesOptions {
   onLocationRequest?: () => void;
   onLocationSync?: () => void;
@@ -51,7 +60,7 @@ export function useServiceWorkerMessages(options: UseServiceWorkerMessagesOption
     }
 
     try {
-      const registration = await navigator.serviceWorker.ready;
+      const registration = await navigator.serviceWorker.ready as ServiceWorkerRegistrationWithSync;
       await registration.sync.register('rmaps-location-sync');
       console.log('[App] Background sync registered');
       return true;