diff --git a/msgpack-rpc.cabal b/msgpack-rpc.cabal
--- a/msgpack-rpc.cabal
+++ b/msgpack-rpc.cabal
@@ -1,5 +1,5 @@
 Name:                msgpack-rpc
-Version:             0.6.0.1
+Version:             0.6.1.0
 Synopsis:            A MessagePack-RPC Implementation
 Description:
   A MessagePack-RPC Implementation <http://msgpack.org/>
@@ -22,7 +22,7 @@
 Library
   Build-depends:     base >= 4 && < 5,
                      bytestring >= 0.9 && < 0.10,
-                     network >= 2.2 && < 2.4,
+                     network >= 2.3 && < 2.4,
                      random >= 1.0 && < 1.1,
                      enumerator >= 0.4 && < 0.5,
                      attoparsec-enumerator >= 0.2 && < 0.3,
diff --git a/src/Network/MessagePackRpc/Client.hs b/src/Network/MessagePackRpc/Client.hs
--- a/src/Network/MessagePackRpc/Client.hs
+++ b/src/Network/MessagePackRpc/Client.hs
@@ -41,6 +41,7 @@
   method,
   ) where
 
+import Control.Concurrent.MVar
 import Control.Exception
 import Control.Monad
 import Data.Attoparsec.Enumerator
@@ -60,7 +61,7 @@
 -- | RPC connection type
 data Connection
   = Connection
-    { connHandle :: Handle }
+    { connHandle :: MVar Handle }
 
 -- | Connect to RPC server
 connect :: String -- ^ Host name
@@ -68,14 +69,15 @@
            -> IO Connection -- ^ Connection
 connect addr port = withSocketsDo $ do
   h <- connectTo addr (PortNumber $ fromIntegral port)
+  mh <- newMVar h
   return $ Connection
-    { connHandle = h
+    { connHandle = mh
     }
 
 -- | Disconnect a connection
 disconnect :: Connection -> IO ()
-disconnect Connection { connHandle = h } =
-  hClose h
+disconnect Connection { connHandle = mh } =
+  hClose =<< takeMVar mh
 
 -- | RPC error type
 data RpcError
@@ -110,7 +112,7 @@
   rpcc c m args arg = rpcc c m (toObject arg:args)
 
 rpcCall :: Connection -> String -> [Object] -> IO Object
-rpcCall Connection{ connHandle = h } m args = do
+rpcCall Connection{ connHandle = mh } m args = withMVar mh $ \h -> do
   msgid <- (`mod`2^(30::Int)) <$> randomIO :: IO Int
   BL.hPutStr h $ pack (0 ::Int, msgid, m, args)
   hFlush h