diff --git a/acconfig.h b/acconfig.h
index 6be883b3f..42532f16f 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -116,6 +116,9 @@ static /**/const char *const rcsid[] = { (char *)rcsid, "\100(#)" msg }
 
 /* telnet stuff ----------------------------------------------- */
 
+/* define this if you have kerberos 4 */
+#undef KRB4
+
 /* define this if you have kerberos 5 */
 #undef KRB5