diff --git a/templates/inspector.html b/templates/inspector.html
index 7780ad2..baf9465 100644
--- a/templates/inspector.html
+++ b/templates/inspector.html
@@ -218,6 +218,7 @@ let _apiData        = null;
 function selectPort(el) {
   const swName = el.dataset.switch;
   const idx    = parseInt(el.dataset.portIdx, 10);
+  if (_diagPollTimer) { clearInterval(_diagPollTimer); _diagPollTimer = null; }
   document.querySelectorAll('.switch-port-block.selected')
     .forEach(e => e.classList.remove('selected'));
   el.classList.add('selected');