diff --git a/Graphics/Win32/LayeredWindow.hsc b/Graphics/Win32/LayeredWindow.hsc
--- a/Graphics/Win32/LayeredWindow.hsc
+++ b/Graphics/Win32/LayeredWindow.hsc
@@ -52,8 +52,13 @@
 foreign import WINDOWS_CCONV unsafe "windows.h UpdateLayeredWindow"
   c_UpdateLayeredWindow :: HANDLE -> HDC -> Ptr POINT -> Ptr SIZE ->  HDC -> Ptr POINT -> COLORREF -> Ptr BLENDFUNCTION -> DWORD -> IO BOOL
 
+#if defined(x86_64_HOST_ARCH)
 foreign import WINDOWS_CCONV "windows.h GetWindowLongPtrW"
   c_GetWindowLongPtr :: HANDLE -> INT -> IO LONG_PTR
+#else
+foreign import WINDOWS_CCONV "windows.h GetWindowLongW"
+  c_GetWindowLongPtr :: HANDLE -> INT -> IO LONG_PTR
+#endif
 
 #{enum DWORD,
  , uLW_ALPHA    = ULW_ALPHA
diff --git a/Graphics/Win32/Menu.hsc b/Graphics/Win32/Menu.hsc
--- a/Graphics/Win32/Menu.hsc
+++ b/Graphics/Win32/Menu.hsc
@@ -446,23 +446,23 @@
 -- Note: these 3 assume the flags don't include MF_BITMAP or MF_OWNERDRAW
 -- (which are hidden by this interface)
 
-appendMenu :: HMENU -> MenuFlag -> MenuID -> String -> IO ()
+appendMenu :: HMENU -> MenuFlag -> MenuID -> Maybe String -> IO ()
 appendMenu menu flags id_item name =
-  withTString name $ \ c_name ->
+  maybeWith withTString name $ \ c_name ->
   failIfFalse_ "AppendMenu" $ c_AppendMenu menu flags id_item c_name
 foreign import WINDOWS_CCONV unsafe "windows.h AppendMenuW"
   c_AppendMenu :: HMENU -> UINT -> MenuID -> LPCTSTR -> IO Bool
 
-insertMenu :: HMENU -> MenuItem -> MenuFlag -> MenuID -> String -> IO ()
+insertMenu :: HMENU -> MenuItem -> MenuFlag -> MenuID -> Maybe String -> IO ()
 insertMenu menu item flags id_item name =
-  withTString name $ \ c_name ->
+  maybeWith withTString name $ \ c_name ->
   failIfFalse_ "InsertMenu" $ c_InsertMenu menu item flags id_item c_name
 foreign import WINDOWS_CCONV unsafe "windows.h InsertMenuW"
   c_InsertMenu :: HMENU -> UINT -> UINT -> MenuID -> LPCTSTR -> IO Bool
 
-modifyMenu :: HMENU -> MenuItem -> MenuFlag -> MenuID -> String -> IO ()
+modifyMenu :: HMENU -> MenuItem -> MenuFlag -> MenuID -> Maybe String -> IO ()
 modifyMenu menu item flags id_item name =
-  withTString name $ \ c_name ->
+  maybeWith withTString name $ \ c_name ->
   failIfFalse_ "ModifyMenu" $ c_ModifyMenu menu item flags id_item c_name
 foreign import WINDOWS_CCONV unsafe "windows.h ModifyMenuW"
   c_ModifyMenu :: HMENU -> UINT -> UINT -> MenuID -> LPCTSTR -> IO Bool
diff --git a/Graphics/Win32/Misc.hsc b/Graphics/Win32/Misc.hsc
--- a/Graphics/Win32/Misc.hsc
+++ b/Graphics/Win32/Misc.hsc
@@ -128,11 +128,11 @@
 
 -- Note: if the error is ever raised, we're in a very sad way!
 
-messageBox :: HWND -> String -> String -> MBStyle -> IO MBStatus
+messageBox :: Maybe HWND -> String -> String -> MBStyle -> IO MBStatus
 messageBox wnd text caption style =
   withTString text $ \ c_text ->
   withTString caption $ \ c_caption ->
-  failIfZero "MessageBox" $ c_MessageBox wnd c_text c_caption style
+  failIfZero "MessageBox" $ c_MessageBox (maybePtr wnd) c_text c_caption style
 foreign import WINDOWS_CCONV safe "windows.h MessageBoxW"
   c_MessageBox :: HWND -> LPCTSTR -> LPCTSTR -> MBStyle -> IO MBStatus
 
diff --git a/Graphics/Win32/Window.hsc b/Graphics/Win32/Window.hsc
--- a/Graphics/Win32/Window.hsc
+++ b/Graphics/Win32/Window.hsc
@@ -23,6 +23,7 @@
 import Data.Maybe (fromMaybe)
 import Data.Int (Int32)
 import Foreign.ForeignPtr (withForeignPtr)
+import Foreign.Marshal.Utils (maybeWith)
 import Foreign.Marshal.Alloc (allocaBytes)
 import Foreign.Ptr (FunPtr, Ptr, castFunPtrToPtr, castPtr, nullPtr)
 import Foreign.Storable (pokeByteOff)
@@ -474,24 +475,24 @@
 foreign import WINDOWS_CCONV unsafe "windows.h EndDeferWindowPos"
   c_EndDeferWindowPos :: HDWP -> IO Bool
 
-findWindow :: String -> String -> IO (Maybe HWND)
+findWindow :: Maybe String -> Maybe String -> IO (Maybe HWND)
 findWindow cname wname =
-  withTString cname $ \ c_cname ->
-  withTString wname $ \ c_wname ->
+  maybeWith withTString cname $ \ c_cname ->
+  maybeWith withTString wname $ \ c_wname ->
   liftM ptrToMaybe $ c_FindWindow c_cname c_wname
 
+{-# DEPRECATED findWindowByName "Use 'findWindow Nothing' instead." #-}
 findWindowByName :: String -> IO (Maybe HWND)
-findWindowByName wname = withTString wname $ \ c_wname ->
-  liftM ptrToMaybe $ c_FindWindow nullPtr c_wname
+findWindowByName wname = findWindow Nothing $ Just wname
 
 foreign import WINDOWS_CCONV unsafe "windows.h FindWindowW"
   c_FindWindow :: LPCTSTR -> LPCTSTR -> IO HWND
 
-findWindowEx :: HWND -> HWND -> String -> String -> IO (Maybe HWND)
+findWindowEx :: Maybe HWND -> Maybe HWND -> Maybe String -> Maybe String -> IO (Maybe HWND)
 findWindowEx parent after cname wname =
-  withTString cname $ \ c_cname ->
-  withTString wname $ \ c_wname ->
-  liftM ptrToMaybe $ c_FindWindowEx parent after c_cname c_wname
+  maybeWith withTString cname $ \ c_cname ->
+  maybeWith withTString wname $ \ c_wname ->
+  liftM ptrToMaybe $ c_FindWindowEx (maybePtr parent) (maybePtr after) c_cname c_wname
 foreign import WINDOWS_CCONV unsafe "windows.h FindWindowExW"
   c_FindWindowEx :: HWND -> HWND -> LPCTSTR -> LPCTSTR -> IO HWND
 
diff --git a/System/Win32/DLL.hsc b/System/Win32/DLL.hsc
--- a/System/Win32/DLL.hsc
+++ b/System/Win32/DLL.hsc
@@ -23,6 +23,7 @@
 
 import Foreign
 import Foreign.C
+import Data.Maybe (fromMaybe)
 
 ##include "windows_cconv.h"
 
@@ -87,10 +88,10 @@
 foreign import WINDOWS_CCONV unsafe "windows.h LoadLibraryExW"
   c_LoadLibraryEx :: LPCTSTR -> HANDLE -> LoadLibraryFlags -> IO HINSTANCE
 
-setDllDirectory :: String -> IO ()
+setDllDirectory :: Maybe String -> IO ()
 setDllDirectory name =
-  withTString name $ \ c_name ->
-  failIfFalse_ (unwords ["SetDllDirectory", name]) $ c_SetDllDirectory c_name
+  maybeWith withTString name $ \ c_name ->
+  failIfFalse_ (unwords ["SetDllDirectory", fromMaybe "NULL" name]) $ c_SetDllDirectory c_name
 
 foreign import WINDOWS_CCONV unsafe "windows.h SetDllDirectoryW"
   c_SetDllDirectory :: LPTSTR -> IO BOOL
diff --git a/System/Win32/File.hsc b/System/Win32/File.hsc
--- a/System/Win32/File.hsc
+++ b/System/Win32/File.hsc
@@ -376,10 +376,10 @@
 foreign import WINDOWS_CCONV unsafe "windows.h MoveFileW"
   c_MoveFile :: LPCTSTR -> LPCTSTR -> IO Bool
 
-moveFileEx :: String -> String -> MoveFileFlag -> IO ()
+moveFileEx :: String -> Maybe String -> MoveFileFlag -> IO ()
 moveFileEx src dest flags =
   withTString src $ \ c_src ->
-  withTString dest $ \ c_dest ->
+  maybeWith withTString dest $ \ c_dest ->
   failIfFalseWithRetry_ (unwords ["MoveFileEx",show src,show dest]) $
     c_MoveFileEx c_src c_dest flags
 foreign import WINDOWS_CCONV unsafe "windows.h MoveFileExW"
@@ -609,9 +609,9 @@
 -- DOS Device flags
 ----------------------------------------------------------------
 
-defineDosDevice :: DefineDosDeviceFlags -> String -> String -> IO ()
+defineDosDevice :: DefineDosDeviceFlags -> String -> Maybe String -> IO ()
 defineDosDevice flags name path =
-  withTString path $ \ c_path ->
+  maybeWith withTString path $ \ c_path ->
   withTString name $ \ c_name ->
   failIfFalse_ "DefineDosDevice" $ c_DefineDosDevice flags c_name c_path
 foreign import WINDOWS_CCONV unsafe "windows.h DefineDosDeviceW"
@@ -661,10 +661,10 @@
 foreign import WINDOWS_CCONV unsafe "windows.h GetDiskFreeSpaceW"
   c_GetDiskFreeSpace :: LPCTSTR -> Ptr DWORD -> Ptr DWORD -> Ptr DWORD -> Ptr DWORD -> IO Bool
 
-setVolumeLabel :: String -> String -> IO ()
+setVolumeLabel :: Maybe String -> Maybe String -> IO ()
 setVolumeLabel path name =
-  withTString path $ \ c_path ->
-  withTString name $ \ c_name ->
+  maybeWith withTString path $ \ c_path ->
+  maybeWith withTString name $ \ c_name ->
   failIfFalse_ "SetVolumeLabel" $ c_SetVolumeLabel c_path c_name
 foreign import WINDOWS_CCONV unsafe "windows.h SetVolumeLabelW"
   c_SetVolumeLabel :: LPCTSTR -> LPCTSTR -> IO Bool
diff --git a/System/Win32/HardLink.hs b/System/Win32/HardLink.hs
--- a/System/Win32/HardLink.hs
+++ b/System/Win32/HardLink.hs
@@ -60,10 +60,10 @@
       , fileSystemName     :: String
       } deriving Show
 
-getVolumeInformation :: String -> IO VolumeInformation
+getVolumeInformation :: Maybe String -> IO VolumeInformation
 getVolumeInformation drive =
-   withTString drive        $ \c_drive ->
-   withTStringBufferLen 256 $ \(vnBuf, vnLen) ->
+   maybeWith withTString drive $ \c_drive ->
+   withTStringBufferLen 256    $ \(vnBuf, vnLen) ->
    alloca $ \serialNum ->
    alloca $ \maxLen ->
    alloca $ \fsFlags ->
diff --git a/System/Win32/Info.hsc b/System/Win32/Info.hsc
--- a/System/Win32/Info.hsc
+++ b/System/Win32/Info.hsc
@@ -21,7 +21,7 @@
 
 import Control.Exception (catch)
 import Foreign.Marshal.Alloc (alloca)
-import Foreign.Marshal.Utils (with)
+import Foreign.Marshal.Utils (with, maybeWith)
 import Foreign.Marshal.Array (allocaArray)
 import Foreign.Ptr (Ptr, nullPtr)
 import Foreign.Storable (Storable(..))
@@ -132,11 +132,11 @@
     try "getShortPathName"
       (c_GetShortPathName c_name) 512
 
-searchPath :: Maybe String -> FilePath -> String -> IO (Maybe FilePath)
+searchPath :: Maybe String -> FilePath -> Maybe String -> IO (Maybe FilePath)
 searchPath path filename ext =
   maybe ($ nullPtr) withTString path $ \p_path ->
   withTString filename $ \p_filename ->
-  withTString ext      $ \p_ext ->
+  maybeWith withTString ext      $ \p_ext ->
   alloca $ \ppFilePart -> (do
     s <- try "searchPath" (\buf len -> c_SearchPath p_path p_filename p_ext
                           len buf ppFilePart) 512
diff --git a/System/Win32/Registry.hsc b/System/Win32/Registry.hsc
--- a/System/Win32/Registry.hsc
+++ b/System/Win32/Registry.hsc
@@ -23,7 +23,7 @@
           regCloseKey        -- :: HKEY -> IO ()
         , regConnectRegistry -- :: Maybe String -> HKEY -> IO HKEY
         , regCreateKey       -- :: HKEY -> String -> IO HKEY
-        , regCreateKeyEx     -- :: HKEY -> String -> String
+        , regCreateKeyEx     -- :: HKEY -> String -> Maybe String
                              -- -> RegCreateOptions -> REGSAM
                              -- -> Maybe LPSECURITY_ATTRIBUTES
                              -- -> IO (HKEY, Bool)
@@ -39,10 +39,10 @@
         , regOpenKey         -- :: HKEY -> String -> IO HKEY
         , regOpenKeyEx       -- :: HKEY -> String -> REGSAM -> IO HKEY
         , regQueryInfoKey    -- :: HKEY -> IO RegInfoKey
-        , regQueryValue      -- :: HKEY -> Maybe String -> IO String
-        , regQueryValueKey   -- :: HKEY -> Maybe String -> IO String
+        , regQueryValue      -- :: HKEY -> String -> IO String
+        , regQueryValueKey   -- :: HKEY -> String -> IO String
         , regQueryValueEx    -- :: HKEY -> String -> Addr -> Int -> IO RegValueType
-        , regReplaceKey      -- :: HKEY -> String -> String -> String -> IO ()
+        , regReplaceKey      -- :: HKEY -> Maybe String -> String -> String -> IO ()
         , regRestoreKey      -- :: HKEY -> String -> RegRestoreFlags -> IO ()
         , regSaveKey         -- :: HKEY -> String -> Maybe LPSECURITY_ATTRIBUTES -> IO ()
         , regSetValue        -- :: HKEY -> String -> String -> IO ()
@@ -144,11 +144,11 @@
  , kEY_WRITE            = KEY_WRITE
  }
 
-regCreateKeyEx :: HKEY -> String -> String -> RegCreateOptions -> REGSAM -> Maybe LPSECURITY_ATTRIBUTES -> IO (HKEY, Bool)
+regCreateKeyEx :: HKEY -> String -> Maybe String -> RegCreateOptions -> REGSAM -> Maybe LPSECURITY_ATTRIBUTES -> IO (HKEY, Bool)
 regCreateKeyEx key subkey cls opts sam mb_attr =
   withForeignPtr key $ \ p_key ->
   withTString subkey $ \ c_subkey ->
-  withTString cls $ \ c_cls ->
+  maybeWith withTString cls $ \ c_cls ->
   alloca $ \ p_res ->
   alloca $ \ p_disp -> do
   failUnlessSuccess "RegCreateKeyEx" $
@@ -387,10 +387,10 @@
 -- (and better!) version of it. If you want RegQueryValue()s
 -- behaviour, use regQueryValueKey.
 
-regQueryValueKey :: HKEY -> Maybe String -> IO String
+regQueryValueKey :: HKEY -> String -> IO String
 regQueryValueKey key mb_subkey =
   withForeignPtr key $ \ p_key ->
-  maybeWith withTString mb_subkey $ \ c_subkey ->
+  withTString mb_subkey $ \ c_subkey ->
   alloca $ \ p_value_len -> do
   failUnlessSuccess "RegQueryValue" $
     c_RegQueryValue p_key c_subkey nullPtr p_value_len
@@ -402,10 +402,10 @@
 foreign import WINDOWS_CCONV unsafe "windows.h RegQueryValueW"
   c_RegQueryValue :: PKEY -> LPCTSTR -> LPTSTR -> Ptr LONG -> IO ErrCode
 
-regQueryValue :: HKEY -> Maybe String -> IO String
+regQueryValue :: HKEY -> String -> IO String
 regQueryValue key mb_subkey =
   withForeignPtr key $ \ p_key ->
-  maybeWith withTString mb_subkey $ \ c_subkey ->
+  withTString mb_subkey $ \ c_subkey ->
   alloca $ \ p_ty ->
   alloca $ \ p_value_len -> do
   failUnlessSuccess "RegQueryValue" $
@@ -430,10 +430,10 @@
 foreign import WINDOWS_CCONV unsafe "windows.h RegQueryValueExW"
   c_RegQueryValueEx :: PKEY -> LPCTSTR -> Ptr DWORD -> Ptr DWORD -> LPBYTE -> Ptr DWORD -> IO ErrCode
 
-regReplaceKey :: HKEY -> String -> String -> String -> IO ()
+regReplaceKey :: HKEY -> Maybe String -> String -> String -> IO ()
 regReplaceKey key subkey newfile oldfile =
   withForeignPtr key $ \ p_key ->
-  withTString subkey $ \ c_subkey ->
+  maybeWith withTString subkey $ \ c_subkey ->
   withTString newfile $ \ c_newfile ->
   withTString oldfile $ \ c_oldfile ->
   failUnlessSuccess "RegReplaceKey" $
diff --git a/System/Win32/Time.hsc b/System/Win32/Time.hsc
--- a/System/Win32/Time.hsc
+++ b/System/Win32/Time.hsc
@@ -30,6 +30,7 @@
                         , with, alloca, allocaBytes, copyArray )
 import Foreign.C        ( CInt(..), CWchar(..)
                         , peekCWString, withCWStringLen, withCWString )
+import Foreign.Marshal.Utils (maybeWith)
 
 ##include "windows_cconv.h"
 #include <windows.h>
@@ -305,10 +306,10 @@
 
 foreign import WINDOWS_CCONV "windows.h GetTimeFormatW"
     c_GetTimeFormat :: LCID -> GetTimeFormatFlags -> Ptr SYSTEMTIME -> LPCTSTR -> LPTSTR -> CInt -> IO CInt
-getTimeFormat :: LCID -> GetTimeFormatFlags -> SYSTEMTIME -> String -> IO String
+getTimeFormat :: LCID -> GetTimeFormatFlags -> Maybe SYSTEMTIME -> Maybe String -> IO String
 getTimeFormat locale flags st fmt =
-    with st $ \c_st ->
-    withCWString fmt $ \c_fmt -> do
+    maybeWith with st $ \c_st ->
+    maybeWith withCWString fmt $ \c_fmt -> do
         size <- c_GetTimeFormat locale flags c_st c_fmt nullPtr 0
         allocaBytes ((fromIntegral size) * (sizeOf (undefined::CWchar))) $ \out -> do
             size' <- failIf (==0) "getTimeFormat: GetTimeFormat" $
diff --git a/System/Win32/Types.hsc b/System/Win32/Types.hsc
--- a/System/Win32/Types.hsc
+++ b/System/Win32/Types.hsc
@@ -209,6 +209,9 @@
 
 type MbHANDLE      = Maybe HANDLE
 
+nullHINSTANCE :: HINSTANCE
+nullHINSTANCE = nullPtr
+
 type   HINSTANCE   = Ptr ()
 type MbHINSTANCE   = Maybe HINSTANCE
 
diff --git a/Win32.cabal b/Win32.cabal
--- a/Win32.cabal
+++ b/Win32.cabal
@@ -1,9 +1,9 @@
 name:		Win32
-version:	2.5.3.0
+version:	2.5.4.0
 license:	BSD3
 license-file:	LICENSE
-author:		Alastair Reid, shelarcy
-copyright:	Alastair Reid, 1999-2003; shelarcy, 2012-2013
+author:		Alastair Reid, shelarcy, Tamar Christina
+copyright:	Alastair Reid, 1999-2003; shelarcy, 2012-2013; Tamar Christina, 2016-2017
 maintainer:	Haskell Libraries <libraries@haskell.org>
 bug-reports:    https://github.com/haskell/win32/issues
 homepage:       https://github.com/haskell/win32
@@ -11,13 +11,23 @@
 synopsis:	A binding to part of the Win32 library
 description:	A binding to part of the Win32 library.
 build-type:     Simple
-cabal-version:  >=1.6
+cabal-version:  >=1.10
 extra-source-files:
 	include/diatemp.h include/dumpBMP.h include/ellipse.h include/errors.h
 	include/Win32Aux.h include/win32debug.h include/alignment.h
         changelog.md
 
 Library
+    default-language: Haskell2010
+    default-extensions: ForeignFunctionInterface, CPP
+    if impl(ghc >= 7.1)
+        default-extensions: NondecreasingIndentation
+
+    if !os(windows)
+        -- This package requires Windows to build
+        build-depends: unbuildable<0
+        buildable: False
+
     build-depends:	base >= 4.5 && < 5, bytestring, filepath
     ghc-options:    -Wall -fno-warn-name-shadowing
     cc-options:     -fno-strict-aliasing
@@ -90,9 +100,6 @@
         System.Win32.Utils
         System.Win32.Word
 
-    extensions:    ForeignFunctionInterface, CPP
-    if impl(ghc >= 7.1)
-        extensions: NondecreasingIndentation
     extra-libraries:
         "user32", "gdi32", "winmm", "advapi32", "shell32", "shfolder", "shlwapi", "msimg32", "imm32"
     ghc-options:      -Wall
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,12 @@
 # Changelog for [`Win32` package](http://hackage.haskell.org/package/Win32)
 
+## Unreleased GIT version
+
+* Make cabal error out on compilation on non-Windows OSes. (See #80)
+* Update cabal format to 1.10 and set language 
+  default to Haskell2010. (See #81)
+* Use `Maybe` in wrappers for functions with nullable pointer parameters (See #83)
+
 ## 2.5.3.0 *March 2017*
 
 * Fix buffer overflow in `regSetValue`. (See #39)