diff --git a/src/System/Console/Terminal/Posix.hsc b/src/System/Console/Terminal/Posix.hsc
index ebca398..204b739 100644
--- a/src/System/Console/Terminal/Posix.hsc
+++ b/src/System/Console/Terminal/Posix.hsc
@@ -4,15 +4,13 @@ module System.Console.Terminal.Posix
   ( size, fdSize, hSize
   ) where
 
+import System.IO (Handle)
+import System.IO.OS (withFileDescriptorReadingBiasedRaw)
 import System.Console.Terminal.Common
 import Control.Exception (catch)
-import Data.Typeable (cast)
 import Foreign
 import Foreign.C.Error
 import Foreign.C.Types
-import GHC.IO.FD (FD(FD, fdFD))
-import GHC.IO.Handle.Internals (withHandle_)
-import GHC.IO.Handle.Types (Handle, Handle__(Handle__, haDevice))
 #if defined(__GLASGOW_HASKELL__) && (__GLASGOW_HASKELL__ < 706)
 import Prelude hiding (catch)
 #endif
@@ -59,7 +57,4 @@ size :: Integral n => IO (Maybe (Window n))
 size = fdSize (Fd (#const STDOUT_FILENO))
 
 hSize :: Integral n => Handle -> IO (Maybe (Window n))
-hSize h = withHandle_ "hSize" h $ \Handle__ { haDevice = dev } ->
-  case cast dev of
-    Nothing -> return Nothing
-    Just FD { fdFD = fd } -> fdSize (Fd fd)
+hSize h = withFileDescriptorReadingBiasedRaw h $ fdSize . Fd