diff --git a/fluent-logger.cabal b/fluent-logger.cabal
--- a/fluent-logger.cabal
+++ b/fluent-logger.cabal
@@ -1,5 +1,5 @@
 name:                fluent-logger
-version:             0.2.3.0
+version:             0.2.3.1
 synopsis:            A structured logger for Fluentd (Haskell)
 description:         A structured logger for Fluentd (Haskell) <http://fluentd.org/>
 license:             Apache-2.0
diff --git a/src/Network/Fluent/Logger.hs b/src/Network/Fluent/Logger.hs
--- a/src/Network/Fluent/Logger.hs
+++ b/src/Network/Fluent/Logger.hs
@@ -31,12 +31,15 @@
 
 import qualified Data.ByteString.Char8 as BS ( ByteString, pack, unpack, empty, null)
 import qualified Data.ByteString.Lazy as LBS ( ByteString, length )
+#if MIN_VERSION_base(4,8,0)
+#else
+import Control.Applicative ( (<$>) )
 import Data.Monoid ( mconcat )
+#endif
 import qualified Network.Socket as NS
 import Network.Socket.Options ( setRecvTimeout, setSendTimeout )
 import Network.Socket.ByteString.Lazy ( sendAll, recv )
 import Control.Monad ( void, forever, when )
-import Control.Applicative ( (<$>) )
 import Control.Concurrent ( ThreadId, killThread, threadDelay )
 import Control.Concurrent.STM ( atomically, orElse
                               , TChan, newTChanIO, readTChan, peekTChan, writeTChan
diff --git a/src/Network/Fluent/Logger/Packable.hs b/src/Network/Fluent/Logger/Packable.hs
--- a/src/Network/Fluent/Logger/Packable.hs
+++ b/src/Network/Fluent/Logger/Packable.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE FlexibleInstances, IncoherentInstances, TypeSynonymInstances #-}
+{-# LANGUAGE CPP #-}
 -- | For compatibility with msgpack
 module Network.Fluent.Logger.Packable (Packable(..)) where
 
@@ -7,6 +8,10 @@
 import qualified Data.Vector as V
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as LT
+#if MIN_VERSION_messagepack(0,4,0)
+import qualified Data.Text.Encoding as T
+import qualified Data.Text.Lazy.Encoding as LT
+#endif
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.ByteString.Lazy as LBS
 
@@ -27,7 +32,11 @@
     pack = ObjectInt . fromIntegral
 
 instance Packable String where
+#if MIN_VERSION_messagepack(0,4,0)
+    pack = ObjectString . BS.pack
+#else
     pack = ObjectString . T.pack
+#endif
 
 instance Packable BS.ByteString where
     pack = ObjectBinary
@@ -36,10 +45,18 @@
     pack = ObjectBinary . LBS.toStrict
 
 instance Packable T.Text where
+#if MIN_VERSION_messagepack(0,4,0)
+    pack = ObjectString . T.encodeUtf8
+#else
     pack = ObjectString
+#endif
 
 instance Packable LT.Text where
+#if MIN_VERSION_messagepack(0,4,0)
+    pack = pack . LT.encodeUtf8
+#else
     pack = ObjectString . T.pack . LT.unpack
+#endif
 
 instance Packable a => Packable [a] where
     pack = ObjectArray . map pack
diff --git a/test/Network/Fluent/Logger/Unpackable.hs b/test/Network/Fluent/Logger/Unpackable.hs
--- a/test/Network/Fluent/Logger/Unpackable.hs
+++ b/test/Network/Fluent/Logger/Unpackable.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE FlexibleInstances, IncoherentInstances, TypeSynonymInstances #-}
 {-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE CPP #-}
 -- | For compatibility with msgpack
 module Network.Fluent.Logger.Unpackable where
 
@@ -9,6 +10,10 @@
 import qualified Data.Map as M
 import qualified Data.Text as T
 import qualified Data.Text.Lazy as LT
+#if MIN_VERSION_messagepack(0,4,0)
+import qualified Data.Text.Encoding as T
+import qualified Data.Text.Lazy.Encoding as LT
+#endif
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.ByteString.Lazy as LBS
 
@@ -37,7 +42,11 @@
     unpack x = throw $ UnpackError $ "invalid for int: " ++ show x
 
 instance Unpackable String where
+#if MIN_VERSION_messagepack(0,4,0)
+    unpack (ObjectString x) = BS.unpack x
+#else
     unpack (ObjectString x) = T.unpack x
+#endif
     unpack x = throw $ UnpackError $ "invalid for string: " ++ show x
 
 instance Unpackable BS.ByteString where
@@ -49,11 +58,19 @@
     unpack x = throw $ UnpackError $ "invalid for binary: " ++ show x
 
 instance Unpackable T.Text where
+#if MIN_VERSION_messagepack(0,4,0)
+    unpack (ObjectString x) = T.decodeUtf8 x
+#else
     unpack (ObjectString x) = x
+#endif
     unpack x = throw $ UnpackError $ "invalid for string: " ++ show x
 
 instance Unpackable LT.Text where
+#if MIN_VERSION_messagepack(0,4,0)
+    unpack x@(ObjectString _) = LT.decodeUtf8 . unpack $ x
+#else
     unpack (ObjectString x) = LT.pack . T.unpack $ x
+#endif
     unpack x = throw $ UnpackError $ "invalid for string: " ++ show x
 
 instance (Unpackable a1, Unpackable a2) => Unpackable (a1, a2) where