diff --git a/mod/chat/gui_header_js/chatinput.php b/mod/chat/gui_header_js/chatinput.php
index 18b35fcecc9..61b72b2c8f5 100644
--- a/mod/chat/gui_header_js/chatinput.php
+++ b/mod/chat/gui_header_js/chatinput.php
@@ -1,6 +1,6 @@
 <?php  // $Id$
 
-    $nomoodlecookie = true;     // Session not needed!
+    define('NO_MOODLE_COOKIES', true); // session not used here
 
     require('../../../config.php');
     require('../lib.php');
@@ -53,7 +53,7 @@
           onsubmit="return empty_field_and_submit()" style="margin:0">
         <input type="text" id="input_chat_message" name="chat_message" size="50" value="" />
         <?php helpbutton('chatting', get_string('helpchatting', 'chat'), 'chat', true, false); ?><br />
-        <input type="checkbox" id="auto" size="50" value="" checked /><?php echo get_string('autoscroll', 'chat');?>
+        <input type="checkbox" id="auto" size="50" value="" checked='true' /><?php echo get_string('autoscroll', 'chat');?>
     </form>
 
     <form action="insert.php" method="post" target="empty" id="sendForm">
diff --git a/mod/chat/gui_header_js/jsupdate.php b/mod/chat/gui_header_js/jsupdate.php
index cd3cc71a53e..87fed99ccef 100644
--- a/mod/chat/gui_header_js/jsupdate.php
+++ b/mod/chat/gui_header_js/jsupdate.php
@@ -1,6 +1,6 @@
 <?php  // $Id$
 
-    $nomoodlecookie = true;     // Session not needed!
+    define('NO_MOODLE_COOKIES', true); // session not used here
 
     require('../../../config.php');
     require('../lib.php');
@@ -143,8 +143,11 @@
             }
         }
         ?>
-        if(parent.msg && parent.input.document.getElementById('auto').checked){
-            parent.msg.scroll(1,5000000);
+        if(parent.input){
+            var autoscroll = parent.input.document.getElementById('auto');
+            if(parent.msg && autoscroll && autoscroll.checked){
+                parent.msg.scroll(1,5000000);
+            }
         }
         //]]>
         </script>