diff --git a/SoObjects/SOGo/SOGoUserManager.m b/SoObjects/SOGo/SOGoUserManager.m
index e2ea77d77..ae323b8cc 100644
--- a/SoObjects/SOGo/SOGoUserManager.m
+++ b/SoObjects/SOGo/SOGoUserManager.m
@@ -1023,7 +1023,7 @@ static Class NSNullK;
     {
       // Remove the "@" prefix used to identified groups in the ACL tables.
       aUID = [uid hasPrefix: @"@"] ? [uid substringFromIndex: 1] : uid;
-      if (domain && [aUID rangeOfString: @"@"].location == NSNotFound)
+      if ([domain length] && [aUID rangeOfString: @"@"].location == NSNotFound)
         cacheUid = [NSString stringWithFormat: @"%@@%@", aUID, domain];
       else
         cacheUid = aUID;