diff --git a/isdnctrl/config.h.in b/isdnctrl/config.h.in
index b9d68884..f29ca439 100644
--- a/isdnctrl/config.h.in
+++ b/isdnctrl/config.h.in
@@ -27,3 +27,5 @@
 /* Define if you have the TIMRU facility.  */
 #undef HAVE_TIMRU
 
+/* Define if you have the CISCOKEEPALIVE code */
+#undef HAVE_CISCOKEEPALIVE