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:             0.6.1.1
+Version:             0.6.1.2
 Synopsis:            A MessagePack-RPC Implementation
 Description:
   A MessagePack-RPC Implementation <http://msgpack.org/>
@@ -27,8 +27,8 @@
                      enumerator >= 0.4 && < 0.5,
                      attoparsec-enumerator >= 0.2 && < 0.3,
                      msgpack >= 0.6 && < 0.7,
-                     transformers >= 0.2 && < 0.3,
-                     deepseq >= 1.1 && < 1.2
+                     mtl >= 2.0 && < 2.1,
+                     deepseq >= 1.1 && < 1.3
 
   Ghc-options:       -Wall
   Hs-source-dirs:    src
diff --git a/src/Network/MessagePackRpc/Server.hs b/src/Network/MessagePackRpc/Server.hs
--- a/src/Network/MessagePackRpc/Server.hs
+++ b/src/Network/MessagePackRpc/Server.hs
@@ -40,7 +40,7 @@
 import Data.Enumerator
 import Data.Enumerator.Binary
 import Control.Monad
-import Control.Monad.IO.Class
+import Control.Monad.Trans
 import Data.Attoparsec.Enumerator
 import qualified Data.ByteString.Lazy as BL
 import Data.Maybe