diff --git a/cmd/zrok/reserve.go b/cmd/zrok/reserve.go
index 2dc28b9e..bf21b664 100644
--- a/cmd/zrok/reserve.go
+++ b/cmd/zrok/reserve.go
@@ -33,7 +33,7 @@ func newReserveCommand() *reserveCommand {
 	command := &reserveCommand{cmd: cmd}
 	cmd.Flags().StringArrayVar(&command.basicAuth, "basic-auth", []string{}, "Basic authentication users (<username:password>,...)")
 	cmd.Flags().StringArrayVar(&command.frontendSelection, "frontends", []string{"public"}, "Selected frontends to use for the share")
-	cmd.Flags().StringVar(&command.backendMode, "backend-mode", "proxy", "The backend mode {proxy, web}")
+	cmd.Flags().StringVar(&command.backendMode, "backend-mode", "proxy", "The backend mode {proxy, web, <tcpTunnel, udpTunnel>}")
 	cmd.Run = command.run
 	return command
 }