diff --git a/Data/MessagePack/Pack.hs b/Data/MessagePack/Pack.hs
--- a/Data/MessagePack/Pack.hs
+++ b/Data/MessagePack/Pack.hs
@@ -34,14 +34,12 @@
 import qualified Data.Text.Lazy as TL
 import qualified Data.Text.Lazy.Encoding as TL
 import qualified Data.Vector as V
-import Foreign
+import Foreign hiding (unsafeLocalState)
+import Foreign.Marshal.Unsafe
 
 import Data.MessagePack.Assoc
 import Data.MessagePack.Internal.Utf8
 
-(<>) :: Monoid m => m -> m -> m
-(<>) = mappend
-
 -- | Serializable class
 class Packable a where
   -- | Serialize a value
@@ -102,7 +100,7 @@
     fromWord64be (cast d)
 
 cast :: (Storable a, Storable b) => a -> b
-cast v = unsafePerformIO $ with v $ peek . castPtr
+cast v = unsafeLocalState $ with v $ peek . castPtr
 
 instance Packable String where
   from = fromString encodeUtf8 B.length fromByteString
diff --git a/msgpack.cabal b/msgpack.cabal
--- a/msgpack.cabal
+++ b/msgpack.cabal
@@ -1,5 +1,5 @@
 Name:               msgpack
-Version:            0.7.0
+Version:            0.7.1
 Synopsis:           A Haskell implementation of MessagePack
 Description:        A Haskell implementation of MessagePack <http://msgpack.org/>
 Homepage:           http://msgpack.org/
@@ -18,18 +18,18 @@
   Location:         git://github.com/msgpack/msgpack-haskell.git
 
 Library
-  Build-depends:    base >=4 && <5
-                  , mtl >= 2.0 && < 2.1
-                  , bytestring >= 0.9 && < 0.10
-                  , text >= 0.11 && < 0.12
-                  , containers >= 0.4 && < 0.5
-                  , unordered-containers >= 0.1 && < 0.2
-                  , hashable >= 1.1 && < 1.2
-                  , vector >= 0.7 && < 0.10
-                  , attoparsec >= 0.8 && < 0.11
+  Build-depends:    base          == 4.*
+                  , mtl           == 2.0.*
+                  , bytestring    == 0.9.*
+                  , text          == 0.11.*
+                  , containers    == 0.4.*
+                  , unordered-containers == 0.1.*
+                  , hashable      == 1.1.*
+                  , vector        >= 0.7 && < 0.10
+                  , attoparsec    >= 0.8 && < 0.11
                   , blaze-builder >= 0.3 && < 0.4
-                  , deepseq >= 1.1 && <1.3
-                  , template-haskell >= 2.4 && < 2.7
+                  , deepseq       >= 1.1 && <1.4
+                  , template-haskell >= 2.4 && < 2.8
 
   Ghc-options:      -Wall
 
@@ -43,19 +43,12 @@
 
 Test-suite msgpack-tests
   Type:             exitcode-stdio-1.0
-  Main-is:          test/Test.hs
-  Build-depends:    base >= 4 && < 5
-                  , mtl >= 2.0 && < 2.1
-                  , bytestring >= 0.9 && < 0.10
-                  , text >= 0.11 && < 0.12
-                  , containers >= 0.4 && < 0.5
-                  , unordered-containers >= 0.1 && < 0.2
-                  , hashable >= 1.1 && < 1.2
-                  , vector >= 0.7 && < 0.10
-                  , attoparsec >= 0.8 && < 0.11
-                  , blaze-builder >= 0.3 && < 0.4
-                  , deepseq >= 1.1 && <1.3
-                  , template-haskell >= 2.4 && < 2.7
-                  , QuickCheck >= 2.4 && < 2.5
-                  , test-framework >= 0.4 && < 0.5
-                  , test-framework-quickcheck2 >= 0.2 && < 0.3
+  Hs-source-dirs:   test
+  Main-is:          Test.hs
+
+  Build-depends:    base           == 4.*
+                  , bytestring     == 0.9.*
+                  , QuickCheck     == 2.4.*
+                  , test-framework == 0.5.*
+                  , test-framework-quickcheck2 == 0.2.*
+                  , msgpack
diff --git a/test/Test.hs b/test/Test.hs
new file mode 100644
--- /dev/null
+++ b/test/Test.hs
@@ -0,0 +1,70 @@
+import Test.Framework
+import Test.Framework.Providers.QuickCheck2
+import Test.QuickCheck
+
+import Control.Monad
+import qualified Data.ByteString.Char8 as B
+import qualified Data.ByteString.Lazy.Char8 as L
+import Data.MessagePack
+
+instance Arbitrary a => Arbitrary (Assoc a) where
+  arbitrary = liftM Assoc arbitrary
+
+mid :: (Packable a, Unpackable a) => a -> a
+mid = unpack . pack
+
+prop_mid_int a = a == mid a
+  where types = a :: Int
+prop_mid_nil a = a == mid a
+  where types = a :: ()
+prop_mid_bool a = a == mid a
+  where types = a :: Bool
+prop_mid_double a = a == mid a
+  where types = a :: Double
+prop_mid_string a = a == mid a
+  where types = a :: String
+prop_mid_bytestring a = B.pack a == mid (B.pack a)
+  where types = a :: String
+prop_mid_lazy_bytestring a = (L.pack a) == mid (L.pack a)
+  where types = a :: String
+prop_mid_array_int a = a == mid a
+  where types = a :: [Int]
+prop_mid_array_string a = a == mid a
+  where types = a :: [String]
+prop_mid_pair2 a = a == mid a
+  where types = a :: (Int, Int)
+prop_mid_pair3 a = a == mid a
+  where types = a :: (Int, Int, Int)
+prop_mid_pair4 a = a == mid a
+  where types = a :: (Int, Int, Int, Int)
+prop_mid_pair5 a = a == mid a
+  where types = a :: (Int, Int, Int, Int, Int)
+prop_mid_list_int_double a = a == mid a
+  where types = a :: [(Int, Double)]
+prop_mid_list_string_string a = a == mid a
+  where types = a :: [(String, String)]
+prop_mid_map_string_int a = a == mid a
+  where types = a :: Assoc [(String,Int)]
+
+tests =
+  [ testGroup "simple"
+    [ testProperty "int" prop_mid_int
+    , testProperty "nil" prop_mid_nil
+    , testProperty "bool" prop_mid_bool
+    , testProperty "double" prop_mid_double
+    , testProperty "string" prop_mid_string
+    , testProperty "bytestring" prop_mid_bytestring
+    , testProperty "lazy-bytestring" prop_mid_lazy_bytestring
+    , testProperty "[int]" prop_mid_array_int
+    , testProperty "[string]" prop_mid_array_string
+    , testProperty "(int, int)" prop_mid_pair2
+    , testProperty "(int, int, int)" prop_mid_pair3
+    , testProperty "(int, int, int, int)" prop_mid_pair4
+    , testProperty "(int, int, int, int, int)" prop_mid_pair5
+    , testProperty "[(int, double)]" prop_mid_list_int_double
+    , testProperty "[(string, string)]" prop_mid_list_string_string
+    , testProperty "Assoc [(string, int)]" prop_mid_map_string_int
+    ]
+  ]
+
+main = defaultMain tests