diff --git a/services/sync/modules/service.js b/services/sync/modules/service.js
index ab6f5619236..bfa74bb0a3c 100644
--- a/services/sync/modules/service.js
+++ b/services/sync/modules/service.js
@@ -150,7 +150,7 @@ WeaveSvc.prototype = {
   _scheduleTimer: null,
 
   get username() {
-    return Svc.Prefs.get("username");
+    return Svc.Prefs.get("username", "");
   },
   set username(value) {
     if (value)