diff --git a/glib/gtypes.h b/glib/gtypes.h
index 7e4c8eaba..22f0538be 100644
--- a/glib/gtypes.h
+++ b/glib/gtypes.h
@@ -183,8 +183,8 @@ typedef const gchar *   (*GTranslateFunc)       (const gchar   *str,
 #if defined (__GNUC__) && (__GNUC__ >= 2) && defined (__OPTIMIZE__)
 
 #  if __GNUC__ >= 4 && defined (__GNUC_MINOR__) && __GNUC_MINOR__ >= 3
-#    define GUINT32_SWAP_LE_BE(val) ((guint32) __builtin_bswap32 ((gint32) val))
-#    define GUINT64_SWAP_LE_BE(val) ((guint64) __builtin_bswap64 ((gint64) val))
+#    define GUINT32_SWAP_LE_BE(val) ((guint32) __builtin_bswap32 ((gint32) (val)))
+#    define GUINT64_SWAP_LE_BE(val) ((guint64) __builtin_bswap64 ((gint64) (val)))
 #  endif
 
 #  if defined (__i386__)