diff --git a/uncloud/hack/mac.py b/uncloud/hack/mac.py
index 4ac05f2..a408103 100755
--- a/uncloud/hack/mac.py
+++ b/uncloud/hack/mac.py
@@ -60,9 +60,6 @@ class MAC(object):
         return ':'.join(format(s, '02x') for s in b)
 
     def get_next(self, vmuuid=None, as_int=False):
-#        if self.free:
-#            return self.free.pop()
-
         last_number = self.last_used_index()
 
         # FIXME: compare to 48bit minus prefix length
@@ -81,7 +78,7 @@ class MAC(object):
         db_entry['mac_address'] = next_mac
 
         self.db.set("used/{}".format(next_mac),
-                    db_entry)
+                    db_entry, as_json=True)
 
         if as_int:
             return next_mac_number
diff --git a/uncloud/hack/main.py b/uncloud/hack/main.py
index ffd0374..2980516 100644
--- a/uncloud/hack/main.py
+++ b/uncloud/hack/main.py
@@ -25,5 +25,4 @@ def main(arguments):
         print(m.last_used_mac())
 
     if arguments['get_new_mac']:
-        m = MAC(config).get_next()
-        print(m.last_used())
+        print(MAC(config).get_next())