diff --git a/services/core/java/com/android/server/notification/NotificationManagerService.java b/services/core/java/com/android/server/notification/NotificationManagerService.java
index c61228dd6bf77..0c35f505fcdd1 100644
--- a/services/core/java/com/android/server/notification/NotificationManagerService.java
+++ b/services/core/java/com/android/server/notification/NotificationManagerService.java
@@ -3813,8 +3813,10 @@ public class NotificationManagerService extends SystemService {
 
         @Override
         public void onUserSwitched(int user) {
-            for (ManagedServiceInfo info : mServices) {
-                unregisterService(info.service, info.userid);
+            synchronized (mNotificationList) {
+                for (ManagedServiceInfo info : mServices) {
+                    unregisterService(info.service, info.userid);
+                }
             }
             registerRanker();
         }