diff --git a/cmd/relaysrv/main.go b/cmd/relaysrv/main.go
index 9d74ca408..2acd267d0 100644
--- a/cmd/relaysrv/main.go
+++ b/cmd/relaysrv/main.go
@@ -59,6 +59,7 @@ func main() {
 	flag.StringVar(&statusAddr, "status-srv", ":22070", "Listen address for status service (blank to disable)")
 	flag.StringVar(&poolAddrs, "pools", defaultPoolAddrs, "Comma separated list of relay pool addresses to join")
 	flag.StringVar(&providedBy, "provided-by", "", "An optional description about who provides the relay")
+	flag.StringVar(&extAddress, "ext-address", "", "An optional address to advertising as being available on.\n\tAllows listening on an unprivileged port with port forwarding from e.g. 443, and be connected to on port 443.")
 
 	flag.Parse()