diff --git a/class/Gini/Database/MySQL.php b/class/Gini/Database/MySQL.php
index 74c76e5..0ec41d1 100644
--- a/class/Gini/Database/MySQL.php
+++ b/class/Gini/Database/MySQL.php
@@ -361,6 +361,9 @@ private function _addRelationSQL($key, $val)
             case 'null':
                 $deleteAction = 'SET NULL';
                 break;
+            case 'default':
+                $deleteAction = 'SET DEFAULT';
+                break;
             default:
                 $deleteAction = 'NO ACTION';
         }
@@ -375,6 +378,9 @@ private function _addRelationSQL($key, $val)
             case 'null':
                 $updateAction = 'SET NULL';
                 break;
+            case 'default':
+                $updateAction = 'SET DEFAULT';
+                break;
             default:
                 $updateAction = 'NO ACTION';
         }