diff --git a/src/wxxt/contrib/xpm/lib/Makefile.in b/src/wxxt/contrib/xpm/lib/Makefile.in
index 733c4753c0..b71402f328 100644
--- a/src/wxxt/contrib/xpm/lib/Makefile.in
+++ b/src/wxxt/contrib/xpm/lib/Makefile.in
@@ -55,7 +55,8 @@ LDFLAGS = $(XLIB)
 
 XPMCC = $(CC)
 
-XPM_CC = $(XPMCC) $(CFLAGS) -c
+# Extra -I to get mzconfig.h:
+XPM_CC = $(XPMCC) $(CFLAGS) -I../../../../mzscheme -c
 
 OBJS= data.@LTO@ create.@LTO@ misc.@LTO@ rgb.@LTO@ \
       scan.@LTO@ parse.@LTO@ hashtab.@LTO@ \
diff --git a/src/wxxt/contrib/xpm/lib/xpmP.h b/src/wxxt/contrib/xpm/lib/xpmP.h
index 39bcc1b97c..5e7e47807e 100644
--- a/src/wxxt/contrib/xpm/lib/xpmP.h
+++ b/src/wxxt/contrib/xpm/lib/xpmP.h
@@ -75,6 +75,14 @@ extern FILE *popen();
 #define bzero(b, len) memset(b, 0, len)
 #endif
 
+/* PLTSCHEME hack: */
+#include "mzconfig.h"
+#ifdef SIZEOF_LONG
+# if SIZEOF_LONG == 8
+#  define LONG64
+# endif
+#endif
+
 /* the following is defined in X11R6 but not in previous versions */
 #ifdef __alpha
 #ifndef LONG64