diff --git a/Crypto/Random/AESCtr.hs b/Crypto/Random/AESCtr.hs
--- a/Crypto/Random/AESCtr.hs
+++ b/Crypto/Random/AESCtr.hs
@@ -41,10 +41,10 @@
 --
 -- By default, this generator will automatically reseed after generating
 -- 1 megabyte of data.
-data AESRNG = AESRNG { aesrngState     :: RNG
+data AESRNG = AESRNG { aesrngState     :: !RNG
                      , aesrngEntropy   :: EntropyPool
-                     , aesrngThreshold :: Int -- ^ in number of generated block
-                     , aesrngCache     :: ByteString }
+                     , aesrngThreshold :: !Int -- ^ in number of generated block
+                     , aesrngCache     :: !ByteString }
 
 instance Show AESRNG where
     show _ = "aesrng[..]"
@@ -55,8 +55,7 @@
     , aesrngEntropy      = entPool
     , aesrngThreshold    = 1024 -- in blocks generated, so 1mb
     , aesrngCache        = B.empty }
-  where rng = RNG entropy cnt 0 key
-        (key, cnt, entropy) = makeParams b
+  where rng = makeRNG b
 
 -- | make an AES RNG from an EntropyPool.
 --
@@ -99,15 +98,10 @@
 reseedThreshold :: AESRNG -> AESRNG
 reseedThreshold rng
     | getNbChunksGenerated (aesrngState rng) >= lvl =
-         let ent = toBytes $ grabEntropy 64 (aesrngEntropy rng)
-          in rng { aesrngState = reseedState ent (aesrngState rng) }
+         let newRngState = makeRNG $ toBytes $ grabEntropy 64 (aesrngEntropy rng)
+          in rng { aesrngState = newRngState }
     | otherwise  = rng
-  where
-        lvl = aesrngThreshold rng
-        reseedState :: ByteString -> RNG -> RNG
-        reseedState b g@(RNG _ cnt1 _ _) = RNG left cnt2 0 key2
-            where -- (r16, _)           = genNextChunk g
-                  (key2, cnt2, left) = makeParams b
+  where lvl = aesrngThreshold rng
 
 instance CPRG AESRNG where
     cprgCreate                      = make
diff --git a/Crypto/Random/AESCtr/Internal.hs b/Crypto/Random/AESCtr/Internal.hs
--- a/Crypto/Random/AESCtr/Internal.hs
+++ b/Crypto/Random/AESCtr/Internal.hs
@@ -15,27 +15,28 @@
 import qualified Data.ByteString as B
 
 {-| An opaque object containing an AES CPRNG -}
-data RNG = RNG
-    {-# UNPACK #-} !ByteString -- left over entropy. can be use to reseed
-    {-# UNPACK #-} !AES.AESIV  -- counter
-    {-# UNPACK #-} !Int        -- number of chunks generated since reseed
-    {-# UNPACK #-} !AES.AES    -- AES context
+data RNG = RNG !AES.AESIV !Int !AES.AES
 
 getNbChunksGenerated :: RNG -> Int
-getNbChunksGenerated (RNG _ _ c _) = c
+getNbChunksGenerated (RNG _ c _) = c
 
-makeParams :: ByteString -> (AES.AES, AES.AESIV, ByteString)
-makeParams b = key `seq` entropy `seq` (key, AES.aesIV_ cnt, entropy)
+makeParams :: ByteString -> (AES.AES, AES.AESIV)
+makeParams b = key `seq` iv `seq` (key, iv)
   where (keyBS, r1) = B.splitAt 32 b
-        (cnt, r2)   = B.splitAt 16 r1
-        !entropy    = B.copy r2
+        (cnt, _)    = B.splitAt 16 r1
         !key        = AES.initAES keyBS
+        !iv         = AES.aesIV_ $ B.copy cnt
 
+makeRNG :: ByteString -> RNG
+makeRNG b = RNG iv 0 key
+  where (key,iv) = makeParams b
+
 chunkSize :: Int
 chunkSize = 1024
 
 genNextChunk :: RNG -> (ByteString, RNG)
-genNextChunk (RNG entropy counter nbChunks key) = (chunk, newrng)
+genNextChunk (RNG counter nbChunks key) =
+    chunk `seq` newrng `seq` (chunk, newrng)
   where
-        newrng = RNG entropy newCounter (nbChunks+1) key
+        newrng = RNG newCounter (nbChunks+1) key
         (chunk,newCounter) = AES.genCounter key counter chunkSize
diff --git a/cprng-aes.cabal b/cprng-aes.cabal
--- a/cprng-aes.cabal
+++ b/cprng-aes.cabal
@@ -1,5 +1,5 @@
 Name:                cprng-aes
-Version:             0.6.0
+Version:             0.6.1
 Description:         
     Simple crypto pseudo-random-number-generator with really good randomness property.
     .