diff --git a/Data/Char8.hs b/Data/Char8.hs
--- a/Data/Char8.hs
+++ b/Data/Char8.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE MagicHash, CPP #-}
 
 -- | Char8 library to be used with Data.ByteString.Char8.
 -- All function assumes that only 8bit part of 'Char' is used
@@ -104,7 +104,11 @@
 isAscii c = _nul <= c && c <= _del
 
 isLatin1 :: Char -> Bool
+#if __GLASGOW_HASKELL__ >= 707
+isLatin1 (C# c#) = isTrue# (ord# c# <=# 0xff#)
+#else
 isLatin1 (C# c#) = ord# c# <=# 0xff#
+#endif
 
 isAsciiUpper :: Char -> Bool
 isAsciiUpper c = 'A' <= c && c <= 'Z'
diff --git a/word8.cabal b/word8.cabal
--- a/word8.cabal
+++ b/word8.cabal
@@ -1,5 +1,5 @@
 Name:                   word8
-Version:                0.0.3
+Version:                0.0.4
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3