diff --git a/Crypto/Internal/Compat.hs b/Crypto/Internal/Compat.hs
index e89a66b..ea53db7 100644
--- a/Crypto/Internal/Compat.hs
+++ b/Crypto/Internal/Compat.hs
@@ -11,9 +11,11 @@
 {-# LANGUAGE CPP #-}
 module Crypto.Internal.Compat
     ( unsafeDoIO
+    , popCount
     ) where
 
 import System.IO.Unsafe
+import Data.Bits (popCount)
 
 -- | perform io for hashes that do allocation and ffi.
 -- unsafeDupablePerformIO is used when possible as the
@@ -26,3 +28,10 @@ unsafeDoIO = unsafeDupablePerformIO
 #else
 unsafeDoIO = unsafePerformIO
 #endif
+
+#if !(MIN_VERSION_base(4,5,0))
+popCount :: Word64 -> Int
+popCount n = loop 0 n
+  where loop c 0 = c
+        loop c i = loop (c + if testBit c 0 then 1 else 0) (i `shiftR` 1)
+#endif
diff --git a/Crypto/KDF/Scrypt.hs b/Crypto/KDF/Scrypt.hs
index a1f3980..55b9f51 100644
--- a/Crypto/KDF/Scrypt.hs
+++ b/Crypto/KDF/Scrypt.hs
@@ -16,7 +16,6 @@ module Crypto.KDF.Scrypt
     ) where
 
 import Data.Word
-import Data.Bits
 import Data.Byteable
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as B
@@ -30,6 +29,7 @@ import System.IO.Unsafe
 
 import Crypto.Hash (SHA256(..))
 import qualified Crypto.KDF.PBKDF2 as PBKDF2
+import Crypto.Internal.Compat (popCount)
 
 -- | Parameters for Scrypt
 data Parameters = Parameters
@@ -44,13 +44,6 @@ data Parameters = Parameters
 foreign import ccall "cryptonite_scrypt_smix"
     ccryptonite_scrypt_smix :: Ptr Word8 -> Word32 -> Word64 -> Ptr Word8 -> Ptr Word8 -> IO ()
 
-#if !(MIN_VERSION_base(4,5,0))
-popCount :: Word64 -> Int
-popCount n = loop 0 n
-  where loop c 0 = c
-        loop c i = loop (c + if testBit c 0 then 1 else 0) (i `shiftR` 1)
-#endif
-
 -- | Generate the scrypt key derivation data
 generate :: Parameters -> B.ByteString
 generate params