diff --git a/primesieve.cabal b/primesieve.cabal
--- a/primesieve.cabal
+++ b/primesieve.cabal
@@ -1,5 +1,5 @@
 name:                primesieve
-version:             0.1.0.1
+version:             0.2.0
 synopsis:            FFI bindings for the primesieve library.
 description:         FFI bindings for the primesieve library.
 homepage:            https://github.com/sighingnow/computations/tree/master/primesieve#readme
@@ -23,7 +23,9 @@
   default-extensions:  NoImplicitPrelude
                      , OverloadedStrings
   build-depends:       base >= 4.7 && < 5
+                     , basement
                      , foundation
+  extra-libraries:     primesieve, stdc++
 
 executable prime-count
   hs-source-dirs:      example
@@ -34,7 +36,6 @@
   build-depends:       base >= 4.7 && < 5
                      , foundation
                      , primesieve
-  extra-libraries:     primesieve
 
 executable prime-example
   hs-source-dirs:      example
@@ -45,4 +46,3 @@
   build-depends:       base >= 4.7 && < 5
                      , foundation
                      , primesieve
-  extra-libraries:     primesieve
diff --git a/src/Math/Prime/FastSieve/FFI.hs b/src/Math/Prime/FastSieve/FFI.hs
--- a/src/Math/Prime/FastSieve/FFI.hs
+++ b/src/Math/Prime/FastSieve/FFI.hs
@@ -1,17 +1,21 @@
 {-# OPTIONS_GHC -Wno-missing-methods #-}
-{-# OPTIONS_GHC -Wno-missing-pattern-synonym-signatures #-}
-{-# OPTIONS_GHC -Wno-missing-signatures #-}
-{-# OPTIONS_GHC -Wno-orphans #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE MagicHash #-}
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 
 module Math.Prime.FastSieve.FFI where
 
+#include "MachDeps.h"
+
+import Basement.Types.Ptr (Ptr (..))
+import Data.Coerce (coerce)
 import Foundation
 import Foundation.Foreign
 import Foundation.Class.Storable
+import Foundation.Primitive (PrimMonad, primAddrRead, primAddrWrite)
 import Foundation.String (fromBytesUnsafe)
+import GHC.Exts (Addr#)
 
 import Foreign.Marshal.Alloc (alloca)
 
@@ -52,7 +56,24 @@
     tcode _ = UINT64
 
 -- | Orphan instance for CSize as Storable.
-instance Storable CSize
+instance Storable CSize where
+    peek (Ptr addr) = primAddrRead addr (Offset 0)
+    poke (Ptr addr) = primAddrWrite addr (Offset 0)
+
+#if WORD_SIZE_IN_BITS == 64
+type CSizeUnderlying = Word64
+#else
+type CSizeUnderlying = Word32
+#endif
+instance PrimType CSize where
+    primAddrRead addr offset =
+        coerce <$> primAddrRead addr (coerce offset :: Offset CSizeUnderlying)
+
+    primAddrWrite addr offset val =
+         primAddrWrite
+             addr
+             (coerce offset :: Offset CSizeUnderlying)
+             (coerce val :: CSizeUnderlying)
 
 foreign import ccall unsafe "primesieve_generate_primes" c_generate_primes
     :: Word64 -> Word64 -> Ptr CSize -> CInt -> IO (Ptr ())