diff --git a/src/main/java/org/gcube/gcat/moderation/thread/social/notifications/SocialNotificationModerationThread.java b/src/main/java/org/gcube/gcat/moderation/thread/social/notifications/SocialNotificationModerationThread.java
index 6b7ea0f..f682f41 100644
--- a/src/main/java/org/gcube/gcat/moderation/thread/social/notifications/SocialNotificationModerationThread.java
+++ b/src/main/java/org/gcube/gcat/moderation/thread/social/notifications/SocialNotificationModerationThread.java
@@ -196,8 +196,10 @@ public class SocialNotificationModerationThread extends ModerationThread {
 		// Adding current ckanUser
 		users.add(CKANUser.getUsernameFromCKANUsername(ckanUser.getName()));
 		
-		// Adding item author
-		users.add(CKANUser.getUsernameFromCKANUsername(itemAuthorCkanUsername));
+		if(itemAuthorCkanUsername!=null) {
+			// Adding item author
+			users.add(CKANUser.getUsernameFromCKANUsername(itemAuthorCkanUsername));
+		}
 		
 		catalogueEvent.setIdsToNotify(users.toArray(new String[users.size()]));
 		catalogueEvent.setIdsAsGroup(false);