diff --git a/src/acconfig.h b/src/acconfig.h
index 108ae1a5d1fa1655ca5cc43b4b66656775d35aa3..baaf3d779ba9c3c8c68905401625a36b140d9a41 100644
--- a/src/acconfig.h
+++ b/src/acconfig.h
@@ -1,5 +1,5 @@
 /*
- * $Id: acconfig.h,v 1.22 1998/05/17 20:39:18 grubba Exp $
+ * $Id: acconfig.h,v 1.23 1998/05/17 22:58:54 grubba Exp $
  */
 #ifndef MACHINE_H
 #define MACHINE_H
@@ -177,6 +177,9 @@
 /* Define if your OS has the union wait. */
 #undef HAVE_UNION_WAIT
 
+/* Define if you have isgraph */
+#undef HAVE_ISGRAPH
+
 /* Define if your cpp supports the ANSI concatenation operator ## */
 #undef HAVE_ANSI_CONCAT