diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 88a71b09..c965e391 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -379,6 +379,7 @@ struct lease_state {
 #define SV_STASH_AGENT_OPTIONS		37
 #define SV_DDNS_TTL			38
 #define SV_DDNS_UPDATE_STYLE		39
+#define SV_ALLOW_CLIENT_UPDATES		40
 
 #if !defined (DEFAULT_DEFAULT_LEASE_TIME)
 # define DEFAULT_DEFAULT_LEASE_TIME 43200