diff --git a/preferences/inc/hook_admin_deleteaccount.inc.php b/preferences/inc/hook_admin_deleteaccount.inc.php
index 330806130f..0ce7122c4e 100755
--- a/preferences/inc/hook_admin_deleteaccount.inc.php
+++ b/preferences/inc/hook_admin_deleteaccount.inc.php
@@ -17,5 +17,8 @@
 		global $phpgw, $account_id;
 	}
 
+	$table_locks = Array('phpgw_preferences');
+	$phpgw->db->lock($table_locks);
 	$phpgw->db->query('DELETE FROM phpgw_preferences WHERE preference_owner='.$account_id,__LINE__,__FILE__);
+	$phpgw->db->unlock();
 ?>