diff --git a/acconfig.h b/acconfig.h
index b20a8bf6de..489b4203c2 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -32,3 +32,6 @@
 
 /* define if catgets() is available */
 #undef HAVE_CATGETS
+
+/* Define if you have the NET_RT_IFLIST sysctl variable. */
+#undef HAVE_IFLIST_SYSCTL