diff --git a/mod/chat/gui_header_js/jsupdate.php b/mod/chat/gui_header_js/jsupdate.php
index 7ac6981c0ff..36908b17c4a 100644
--- a/mod/chat/gui_header_js/jsupdate.php
+++ b/mod/chat/gui_header_js/jsupdate.php
@@ -49,6 +49,13 @@
         <meta http-equiv="content-type" content="text/html; charset=<?php echo get_string('thischarset'); ?>" />
         <script type="text/javascript">
         <!--
+        if (parent.msg.document.getElementById("msgStarted") == null) {
+            parent.msg.document.close();
+            parent.msg.document.open("text/html","replace");
+            parent.msg.document.write("<html><head>");
+            parent.msg.document.write("<meta http-equiv=\"content-type\" content=\"text/html; charset=<?php echo get_string('thischarset'); ?>\" />");
+            parent.msg.document.write("</head><body><div style=\"display: none\" id=\"msgStarted\">&nbsp;</div>");
+        }
         <?php
         $beep = false;
         $refreshusers = false;
