I've been banging my head on the same issues. To summarise: GHC 6.12 strings are unicode; unix file paths are slightly restricted byte strings; the former is used to represent the latter, leading to great confusion; the best way to fix it is unclear. Here's a workaround I wrote this morning: -- | A platform string is a string value from or for the operating system, -- such as a file path or command-line argument (or environment variable's -- name or value ?). On some platforms (such as unix) these are not real -- unicode strings but have some encoding such as UTF-8. This alias does -- no type enforcement but aids code clarity. type PlatformString = String -- | Convert a possibly encoded platform string to a real unicode string. -- We decode the UTF-8 encoding recommended for unix systems -- (cf http://www.dwheeler.com/essays/fixing-unix-linux-filenames.html) -- and leave anything else unchanged. fromPlatformString :: PlatformString -> String fromPlatformString s = if UTF8.isUTF8Encoded s then UTF8.decodeString s else s -- | Convert a unicode string to a possibly encoded platform string. -- On unix we encode with the recommended UTF-8 -- (cf http://www.dwheeler.com/essays/fixing-unix-linux-filenames.html) -- and elsewhere we leave it unchanged. toPlatformString :: String -> PlatformString toPlatformString = case os of "unix" -> UTF8.encodeString "linux" -> UTF8.encodeString "darwin" -> UTF8.encodeString _ -> id