diff --git a/norikraclient/client.py b/norikraclient/client.py
index 1da4060..f17cf72 100644
--- a/norikraclient/client.py
+++ b/norikraclient/client.py
@@ -13,7 +13,7 @@
 class Client(object):
 
     def __init__(self, host="localhost", port=RPC_DEFAULT_PORT, opts={}):
-        addr = "http://{}:{}/".format(host, port)
+        addr = "http://{0}:{1}/".format(host,port)
         self.addr = addr
         self.client = MsgPackClientOverHttp(addr)