jQuery UI widget factory _on hates events with hyphens.. ?

HTML

<link rel="stylesheet" href="//code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css">
<script src="//code.jquery.com/ui/1.10.3/jquery-ui.js"></script>
<div id="thing">thing</div>

JavaScript

// Custom events with hashes in their name don't get triggered??
$.widget('ui.Thing', {
    _create: function () {
        this.element.text('THING LIVES');
        this._on({
            'click': function () {
                var text = this.element.text();
                this.element.text(text + ' click!');
            },
                'foo': function () {
                var text = this.element.text();
                this.element.text(text + ' foo!');
            },
                'foo-bar': function () {
                var text = this.element.text();
                this.element.text(text + ' FOO-BAR??');
            }
        });
        var that = this;
        this.element.on('phu-baz', function () {
            var text = that.element.text();
            that.element.text(text + ' PHU-BAZ?????');
        });
    }
});

$('#thing').
    Thing().
    trigger('click'). // works! :D
    trigger('foo'). // works! :D
    trigger('foo-bar'). // ..doesn't work?? :/
    trigger('phu-baz'); // ... but THIS works??!? (╯°□°）╯︵ ┻━┻