--- src/m/ibms390x.h
+++ src/m/ibms390x.h	2012-06-26 17:21:34.240010197 +0000
@@ -29,4 +29,8 @@ along with GNU Emacs.  If not, see <http
 #define VALBITS         60
 
 /* Define XPNTR to avoid or'ing with DATA_SEG_BITS */
-#define XPNTR(a) XUINT (a)
+
+#undef DATA_SEG_BITS
+#ifdef USE_LISP_UNION_TYPE
+#undef USE_LISP_UNION_TYPE
+#endif