diff --git a/include/X11/Xtos.h b/include/X11/Xtos.h
index 7079321..9572237 100644
--- a/include/X11/Xtos.h
+++ b/include/X11/Xtos.h
@@ -62,7 +62,8 @@ SOFTWARE.
     defined(__sparc64__) || \
     defined(__s390x__) || \
     (defined(__hppa__) && defined(__LP64__)) || \
-    defined(__amd64__) || defined(amd64) || \
+    (defined(__amd64__) && defined(__LP64__)) /* skip x32 */ || \
+    defined(amd64) || \
     defined(__powerpc64__) || \
     (defined(sgi) && (_MIPS_SZLONG == 64))
 #define LONG64