$.parseXML not working with valid xml

XML:

<?xml version="1.0"?>
<choices>
    <choice>
        <start>39</start>
        <duration>6</duration>
        <path>
            <name></name>
            <complete></complete>
        </path>
        <path>
            <name></name>
            <complete></complete>
        </path>
    </choice>
</choices>

$.ajax({
    url: 'choices.xml',
    context: this,
    async: false,
    success: function(response) {
        var xmlDoc = $.parseXML(response);
        console.log(xmlDoc); // null
    }
});

The XML is reported as valid, and no error is thrown. I know I can use $(response), but I don't need that.

• jQuery 1.7.2