diff --git a/cmd/mtwebmapper/web/index.html b/cmd/mtwebmapper/web/index.html
index 19b02d8..d955a7c 100644
--- a/cmd/mtwebmapper/web/index.html
+++ b/cmd/mtwebmapper/web/index.html
@@ -96,7 +96,7 @@ L.control.coordinates({
 }).addTo(map);
 
 var manualUpdateControl;
-if (window.WebSocket && useWebsocket) {
+if (useWebsocket && 'WebSocket' in window) {
     L.autoUpdate('autoUpdate', function(pressed) {
         if (pressed) {
             manualUpdateControl.getContainer().style = 'visibility: hidden';
diff --git a/cmd/mtwebmapper/web/js/auto-update.js b/cmd/mtwebmapper/web/js/auto-update.js
index a689bc2..d9a2d91 100644
--- a/cmd/mtwebmapper/web/js/auto-update.js
+++ b/cmd/mtwebmapper/web/js/auto-update.js
@@ -45,7 +45,7 @@ L.Control.AutoUpdate = L.Control.extend({
         this.socket.onmessage = function(evt) {
 
             var invalidate = function(json) {
-                var invalidateAll = function(x, y, z) { return true };
+                var invalidateAll = function(x, y, z) { return true; };
 
                 if (!(typeof json === "string")) {
                     return invalidateAll;