diff --git a/src/Language/Hi/Binary.hs b/src/Language/Hi/Binary.hs
index 8b43ac9..7f6dbed 100644
--- a/src/Language/Hi/Binary.hs
+++ b/src/Language/Hi/Binary.hs
@@ -472,7 +472,11 @@ lazyGet bh = do
 -- --------------------------------------------------------------
 
 initBinMemSize       = (1024*1024) :: Int
+#if   WORD_SIZE_IN_BITS == 32
 binaryInterfaceMagic = 0x1face :: Word32
+#elif WORD_SIZE_IN_BITS == 64
+binaryInterfaceMagic = 0x1face64 :: Word32
+#endif
 
 getBinFileWithDict :: Binary a => FilePath -> IO a
 getBinFileWithDict file_path = do