diff --git a/HCodecs.cabal b/HCodecs.cabal
--- a/HCodecs.cabal
+++ b/HCodecs.cabal
@@ -1,5 +1,5 @@
 name: HCodecs
-version: 0.4
+version: 0.4.1
 cabal-Version: >= 1.8
 license: BSD3
 license-file: LICENSE
@@ -33,6 +33,7 @@
   other-modules:
     Internal.ByteString.Parser
     Internal.ByteString.Builder
+    Internal.Arbitrary
 
 test-suite tests
   type: exitcode-stdio-1.0
diff --git a/src/Internal/Arbitrary.hs b/src/Internal/Arbitrary.hs
new file mode 100644
--- /dev/null
+++ b/src/Internal/Arbitrary.hs
@@ -0,0 +1,101 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      : Data.Arbitrary
+-- Copyright   : George Giorgidze
+-- License     : BSD3
+--
+-- Maintainer  : George Giorgidze <http://cs.nott.ac.uk/~ggg/>
+-- Stability   : Experimental
+-- Portability : Portable
+--
+-- Additional instances of the 'Arbitrary' type class defined in 'Test.QuickCheck'.
+-- Some portions of code were copied from the test suite of 'binary' package.
+--
+-----------------------------------------------------------------------------
+
+{-# LANGUAGE FlexibleContexts #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
+module Internal.Arbitrary (
+    arrayGen
+  , stringNulGen
+  ) where
+
+
+import Test.QuickCheck
+
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Lazy as L
+
+import Data.Word
+import Data.Int
+import Data.Char
+
+import Data.List
+import Data.Array.IArray
+
+import System.Random ()
+
+instance Arbitrary Word8 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Word16 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Word32 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Word64 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Int8 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Int16 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Int32 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Int64 where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Word where
+    arbitrary       = choose (minBound, maxBound)
+    coarbitrary     = undefined
+
+instance Arbitrary Char where
+    arbitrary = choose (0, 255) >>= return . toEnum
+    coarbitrary = undefined
+
+instance Arbitrary L.ByteString where
+    arbitrary     = arbitrary >>= return . L.fromChunks . filter (not. B.null)
+    coarbitrary s = coarbitrary (L.unpack s)
+
+instance Arbitrary B.ByteString where
+  arbitrary = B.pack `fmap` arbitrary
+  coarbitrary s = coarbitrary (B.unpack s)
+  
+instance (Arbitrary e, Num i, IArray Array e, Ix i) =>  Arbitrary (Array i e) where
+  arbitrary = do
+    n <- choose (1, 128)
+    arrayGen n
+  coarbitrary = undefined
+
+arrayGen :: (Arbitrary e, Num i, IArray a e, Ix i) => Word -> Gen (a i e)
+arrayGen 0 = error "Array with 0 elements can not be defined"
+arrayGen n = do
+  es <- vector (fromIntegral n)
+  return $! listArray (0 , fromIntegral $ n - 1) es
+  
+stringNulGen :: Word -> Gen String
+stringNulGen n = do
+  sequence $ genericReplicate n $ choose (1,255) >>= return . chr