diff --git a/cmd/strelaypoolsrv/main.go b/cmd/strelaypoolsrv/main.go
index fdaf73de..23ddf4d9 100644
--- a/cmd/strelaypoolsrv/main.go
+++ b/cmd/strelaypoolsrv/main.go
@@ -326,8 +326,9 @@ func handlePostRequest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	ip := net.ParseIP(host)
 	// The client did not provide an IP address, use the IP address of the client.
-	if host == "" {
+	if ip == nil || ip.IsUnspecified() {
 		uri.Host = net.JoinHostPort(rhost, port)
 		newRelay.URL = uri.String()
 	} else if host != rhost {