diff --git a/uncloud/hack/mac.py b/uncloud/hack/mac.py
index 66286dd..e35cd9f 100755
--- a/uncloud/hack/mac.py
+++ b/uncloud/hack/mac.py
@@ -46,7 +46,9 @@ class MAC(object):
     @staticmethod
     def validate_mac(mac):
         if not re.match(r'([0-9A-F]{2}[-:]){5}[0-9A-F]{2}$', mac, re.I):
-            raise Error("Not a valid mac address: %s" % mac)
+            raise UncloudException("Not a valid mac address: %s" % mac)
+        else:
+            return True
 
     def last_used_index(self):
         if not self.no_db: