diff --git a/aiomysql/pool.py b/aiomysql/pool.py
index eaaddbe0..c7979504 100644
--- a/aiomysql/pool.py
+++ b/aiomysql/pool.py
@@ -121,7 +121,7 @@ async def wait_closed(self):
 
         while self._free:
             conn = self._free.popleft()
-            conn.close()
+            await conn.ensure_closed()
 
         async with self._cond:
             while self.size > self.freesize: