diff --git a/acconfig.h b/acconfig.h
index 67f61e04e12..7f4077c34b2 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -25,6 +25,9 @@
 /* Define this if your time.h defines altzone */
 #undef HAVE_ALTZONE
 
+/* Define this if you have a K&R style C preprocessor */
+#undef HAVE_OLD_CPP
+
 /* Define if your compiler supports function prototypes */
 #undef HAVE_PROTOTYPES