2 files changed, 4 insertions, 3 deletions
diff --git a/src/main/java/org/traccar/database/NotificationManager.java b/src/main/java/org/traccar/database/NotificationManager.java
index 45263ff3c..65437f0a1 100644
--- a/src/main/java/org/traccar/database/NotificationManager.java
+++ b/src/main/java/org/traccar/database/NotificationManager.java
@@ -87,7 +87,7 @@ public class NotificationManager {
             return;
         }
 
-        var notifications = cacheManager.getDeviceNotifications(event.getDeviceId())
+        var notifications = cacheManager.getDeviceNotifications(event.getDeviceId()).stream()
                 .filter(notification -> notification.getType().equals(event.getType()))
                 .filter(notification -> {
                     if (event.getType().equals(Event.TYPE_ALARM)) {
diff --git a/src/main/java/org/traccar/session/cache/CacheManager.java b/src/main/java/org/traccar/session/cache/CacheManager.java
index bb9b4c995..89b25af2f 100644
--- a/src/main/java/org/traccar/session/cache/CacheManager.java
+++ b/src/main/java/org/traccar/session/cache/CacheManager.java
@@ -136,14 +136,15 @@ public class CacheManager implements BroadcastInterface {
         }
     }
 
-    public Stream<Notification> getDeviceNotifications(long deviceId) {
+    public Set<Notification> getDeviceNotifications(long deviceId) {
         try {
             lock.readLock().lock();
             var direct = graph.getObjects(Device.class, deviceId, Notification.class, Set.of(Group.class), true)
                     .map(BaseModel::getId)
                     .collect(Collectors.toUnmodifiableSet());
             return graph.getObjects(Device.class, deviceId, Notification.class, Set.of(Group.class, User.class), true)
-                    .filter(notification -> notification.getAlways() || direct.contains(notification.getId()));
+                    .filter(notification -> notification.getAlways() || direct.contains(notification.getId()))
+                    .collect(Collectors.toUnmodifiableSet());
         } finally {
             lock.readLock().unlock();
         }