diff --git a/web/app.js b/web/app.js
index bf689bc..ef27c76 100644
--- a/web/app.js
+++ b/web/app.js
@@ -204,7 +204,9 @@ function hideEditForm(cell) {
 function confirmEditForm(cell) {
   var mac = cell.dataset.mac;
   var ip = cell.dataset.ip;
-  var hostname = cell.querySelector('.edit-hostname').value.trim();
+  var input = cell.querySelector('.edit-hostname');
+  if (!input) return;
+  var hostname = input.value.trim();
   hideEditForm(cell);
   updateHostname(mac, ip, hostname);
 }