diff --git a/src/main/java/org/olat/user/UserManagerImpl.java b/src/main/java/org/olat/user/UserManagerImpl.java
index da0b278e3d21a1d4c4d06e22730599c9bd9231ed..9cf2ede8c1bffefebad01f4c2b69b31db45b4921 100644
--- a/src/main/java/org/olat/user/UserManagerImpl.java
+++ b/src/main/java/org/olat/user/UserManagerImpl.java
@@ -514,8 +514,12 @@ public class UserManagerImpl extends UserManager {
 	}
 	
 	private void updateUsernameCache(Long identityKey, String username, String fullName) {
-		usernameCache.put(identityKey, fullName);
-		usernameCache.put(username, fullName);
+		if(identityKey != null && fullName != null) {
+			usernameCache.put(identityKey, fullName);
+		}
+		if(username != null && fullName != null) {
+			usernameCache.put(username, fullName);
+		}
 	}
 
 	/**