diff --git a/gui/preload-main.js b/gui/preload-main.js
index 373a97e4..c0c52235 100644
--- a/gui/preload-main.js
+++ b/gui/preload-main.js
@@ -623,7 +623,7 @@ document.getElementById('hamlib_rigctld_start').addEventListener('click', () =>
     }
 
     var hamlib_rigctld_server_port = document.getElementById("hamlib_rigctld_server_port").value;
-    paramList = paramList.concat('--port=', hamlib_rigctld_server_port)
+    paramList = paramList.concat('-t', hamlib_rigctld_server_port)