diff --git a/src/Data/TypeHash.hs b/src/Data/TypeHash.hs
--- a/src/Data/TypeHash.hs
+++ b/src/Data/TypeHash.hs
@@ -17,12 +17,14 @@
 module Data.TypeHash(TypeCode, typeCode,
 		     convertibleIso, convertibleWithReadShow, convertibleWithJSON,
                      TypeHash, typeHash) where
-import Data.Char(isAlpha)
+import Control.Arrow((***))
 import Control.Monad.State
-import Data.Generics
 import Data.Binary
-import Data.Digest.Pure.MD5(MD5Digest, md5)
 import Data.ByteString.Lazy(pack)
+import Data.Char(isAlpha)
+import Data.Digest.Pure.MD5(MD5Digest, md5)
+import Data.Generics
+import Data.Typeable.Internal(tyConModule, tyConName)
 
 --import Debug.Trace
 
@@ -65,12 +67,20 @@
         f = do modify (gType tns (undefined :: d) :); return undefined
 
 -- Replace unqualified type name by qualified type name.
--- XXX Only does it on the top level, because I don't know how to get deeper.
+-- XXX ?not yet? Also replace some ghc specific names with more portable ones.
 fullTypeOf :: (Data a) => a -> TypeRep
-fullTypeOf a | not $ isAlpha $ head $ tyConString $ typeRepTyCon $ ta = ta
-	     | otherwise = mkTyConApp (mkTyCon $ dataTypeName $ dataTypeOf a)
-                                      (typeRepArgs ta)
-  where ta = typeOf a
+fullTypeOf = fixup . typeOf
+  where fixup = uncurry mkTyConApp . (fixupTyCon *** map fixup) . splitTyConApp
+        fixupTyCon c = mkTyCon $
+            case (tyConModule c, tyConName c) of
+{-
+            ("GHC.Types", s)                -> "Prelude." ++ s
+            ("GHC.Tuple", s)                -> "Prelude." ++ s
+            ("GHC.Unit", "()")              -> "Prelude.()"
+            ("GHC.Integer.Type", "Integer") -> "Prelude.Integer"
+-}
+            (m, s)                          -> m ++ "." ++ s
+
 
 ------------
 
diff --git a/typehash.cabal b/typehash.cabal
--- a/typehash.cabal
+++ b/typehash.cabal
@@ -1,6 +1,6 @@
 Name:           typehash
 Cabal-Version:  >= 1.2
-Version:        1.4.0.2
+Version:        1.4.0.3
 License:        BSD3
 Author:         Lennart Augustsson
 Maintainer:     Lennart Augustsson
@@ -14,5 +14,5 @@
 
 Library
   Hs-Source-Dirs: src
-  Build-Depends: base >= 4 && < 4.4, syb, mtl, bytestring, pureMD5, binary
+  Build-Depends: base >= 4 && < 4.5, syb, mtl, bytestring, pureMD5, binary
   Exposed-modules:      Data.TypeHash