Why is my jQuery taphold event firing twice?

Question

I'm attempting to use jQuery's Sortable widget on a mobile device (jquery-mobile/jquery-touch-punch). However the taphold event fires twice with this setup (but just the once on non-touch devices).

<ul id="sortable">
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
</ul>

$(function () {
    $("#sortable").sortable({
        axis: "y",
        revert: 100
    });
    $("#sortable").on("taphold", function () {
        alert("Taphold fired"); // fires twice on touch devices
    });
});

Fiddle: http://jsfiddle.net/obft7wrg/2/