--- include/net-snmp/system/freebsd13.h.orig	2018-12-25 15:35:28 UTC
+++ include/net-snmp/system/freebsd13.h
@@ -0,0 +1,3 @@
+/* freebsd13 is a superset of freebsd12 */
+#include "freebsd12.h"
+#define freebsd13 freebsd13
