jquery tagit: prepoluate with tags not working if there's a custom autocomplete source

Question

I read the docs and if you want to prepoulate with some tags, you can use an ul element:

<ul id="myULTags">
    <li>Tag1</li>
    <li>Tag2</li>
</ul>

But the thing is that i use a custom autocomplete source like this:

$("#myULTags").tagit({
            allowSpaces: true, autocomplete: {
                delay: 500, minLength: 1, source: function (request, response) {
                    $.ajax({
                        url: '/controller/method/',
                        type: 'GET',
                        dataType: 'json',
                        async: false,
                        cache: false,
                        data: { Campo: request.term },
                        success: function (dados) {
                            let data = JSON.parse(JSON.stringify(dados));
                            currentlyValidTags = data;
                            response($.map(data, function (item) {
                                return {
                                    label: item,
                                    value: item
                                };
                            }));
                        },
                        failure: function (response) {
                            currentlyValidTags = [];
                            return [];
                        },
                        error: function (response) {
                            currentlyValidTags = [];
                            return [];
                        }
                    });
                }
            },
            beforeTagAdded: function (event, ui) {
                if ($.inArray(ui.tagLabel, currentlyValidTags) == -1) {
                    return false;
                }
            }
        });

And as the result, my prepopulated tags get overridden. Is there a way to prepopulate my tagit component AND use the custom autocomplete source?