diff --git a/phpBB/includes/acp/acp_groups.php b/phpBB/includes/acp/acp_groups.php
index 279fb7f56d..1680dacfda 100644
--- a/phpBB/includes/acp/acp_groups.php
+++ b/phpBB/includes/acp/acp_groups.php
@@ -179,13 +179,16 @@ class acp_groups
 
 			case 'deleteusers':
 			case 'delete':
+    			if (!$group_id)
+				{
+					trigger_error($user->lang['NO_GROUP'] . adm_back_link($this->u_action), E_USER_WARNING);
+				}
+				else if ($action === 'delete' && $group_row['group_type'] == GROUP_SPECIAL)
+				{
+					trigger_error($user->lang['NO_AUTH_OPERATION'] . adm_back_link($this->u_action), E_USER_WARNING);
+				}
 				if (confirm_box(true))
 				{
-					if (!$group_id)
-					{
-						trigger_error($user->lang['NO_GROUP'] . adm_back_link($this->u_action), E_USER_WARNING);
-					}
-
 					$error = '';
 
 					switch ($action)