IE9 jqXHR.responseXML returns "undefined"

IE9 jqXHR.responseXML returns "undefined" while FireFox 3.6.13 correctly returns: [object XMLDocument]

HTML

<html>
<head>
<meta http-equiv="content-type"      content="text/html; charset=utf-16"/>
<head>
<title>Hello</title>
</head>
<body>
</body>
</html>

JavaScript

$.ajax({
     url: "/echo/xml",
     dataType: "xml",
     complete: function(jqXHR) {
         alert("jqXHR.responseText = " + jqXHR.responseText);
         alert("jqXHR.responseXML = " + jqXHR.responseXML);
     }
 });