diff --git a/Crypto/Random/Entropy/Unix.hs b/Crypto/Random/Entropy/Unix.hs
index 9a7400c..a8aae43 100644
--- a/Crypto/Random/Entropy/Unix.hs
+++ b/Crypto/Random/Entropy/Unix.hs
@@ -58,7 +58,7 @@ withDev :: String -> (H -> IO a) -> IO a
 withDev filepath f = openDev filepath >>= \h ->
     case h of
         Nothing -> error ("device " ++ filepath ++ " cannot be grabbed")
-        Just fd -> f fd >>= \r -> (closeDev fd >> return r)
+        Just fd -> f fd `E.finally` closeDev fd
 
 closeDev :: H -> IO ()
 closeDev h = hClose h