IE9 jqXHR.responseXML returns "undefined"

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

by jaubourg

HTML

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

JavaScript

$.ajaxPrefilter(function( options, _, jqXHR ) {
    var oldXHR = options.xhr,
        xhr;
    options.xhr = function() {
        return xhr = oldXHR.apply( options, arguments );
    };
    jqXHR.complete(function() {
         alert("xhr.responseText = " + xhr.responseText);
         alert("xhr.responseXML = " + xhr.responseXML);
    });
});

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