--- src/m/ibms390x.h
+++ src/m/ibms390x.h	2011-07-11 11:51:06.080426771 +0000
@@ -78,7 +78,9 @@ NOTE-END */
    working alloca function and it should be used.  Undefine it if an
    assembler-language alloca in the file alloca.s should be used. */
 
+#ifndef HAVE_ALLOCA
 #define HAVE_ALLOCA
+#endif
 
 /* On the 64 bit architecture, we can use 60 bits for addresses */
 
@@ -88,7 +90,10 @@ NOTE-END */
 
 /* 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
 
 #undef START_FILES
 #define START_FILES pre-crt0.o $(CRT_DIR)/crt1.o $(CRT_DIR)/crti.o