diff --git a/lib/dns/include/dns/events.h b/lib/dns/include/dns/events.h
index 1cd90dfe84..9232c0080c 100644
--- a/lib/dns/include/dns/events.h
+++ b/lib/dns/include/dns/events.h
@@ -48,6 +48,7 @@ ISC_LANG_BEGINDECLS
 #define DNS_EVENT_DBDESTROYED			(ISC_EVENTCLASS_DNS + 18)
 #define DNS_EVENT_VALIDATORDONE			(ISC_EVENTCLASS_DNS + 19)
 #define DNS_EVENT_REQUESTDONE			(ISC_EVENTCLASS_DNS + 20)
+#define DNS_EVENT_VALIDATORSTART		(ISC_EVENTCLASS_DNS + 21)
 
 #define DNS_EVENT_FIRSTEVENT			(ISC_EVENTCLASS_DNS + 0)
 #define DNS_EVENT_LASTEVENT			(ISC_EVENTCLASS_DNS + 65535)