diff --git a/kfet/templates/kfet/history.html b/kfet/templates/kfet/history.html
index 64ccf23d..c4b458bf 100644
--- a/kfet/templates/kfet/history.html
+++ b/kfet/templates/kfet/history.html
@@ -63,6 +63,7 @@
 
 <script type="text/javascript">
 $(document).ready(function() {
+    'use strict';
 
     // Lock to avoid multiple requests
     window.lock = 0;
@@ -138,12 +139,12 @@ $(document).ready(function() {
     // Synchronization
     // -----
 
-    websocket_msg_default = {'opegroups':[],'opes':[]}
+    var websocket_msg_default = {'opegroups':[],'opes':[]}
 
     var websocket_protocol = window.location.protocol == 'https:' ? 'wss' : 'ws';
     var location_host = window.location.host;
     var location_url = window.location.pathname.startsWith('/gestion/') ? location_host + '/gestion' : location_host;
-    socket = new ReconnectingWebSocket(websocket_protocol+"://" + location_url + "/ws/k-fet/k-psul/");
+    var socket = new ReconnectingWebSocket(websocket_protocol+"://" + location_url + "/ws/k-fet/k-psul/");
     socket.onmessage = function(e) {
         data = $.extend({}, websocket_msg_default, JSON.parse(e.data));
         history.update_data(data);