diff --git a/tornado_mysql/pools.py b/tornado_mysql/pools.py
index f7c4b69..db6048b 100644
--- a/tornado_mysql/pools.py
+++ b/tornado_mysql/pools.py
@@ -169,7 +169,7 @@ def _close(self):
         self._pool = self._conn = None
 
     @coroutine
-    def execute(self, query, args):
+    def execute(self, query, args=None):
         """
         :return: Future[Cursor]
         :rtype: Future