I use bootstrap multi-select and I want to update options on flow with ajax

To populate on init my multiselect I do

<select name=model class=multiselect multiple=multiple>

                <? foreach ($sel_models as $mod) { ?>

                    <option value=<?= $mod ?> <?= ($mod == $params['model']) ? 'selected' : '' ?>><?= $mod ?></option>

                <? } ?>    

</select>  

then on event I would like to update my option list with the following ajax

I was trying to use the rebuild method but won't fire the drop-down after creation

 $.ajax({

        type: 'post',

        url: helper/ajax_search.php,

        data: {models: decodeURIComponent(brands)},

        dataType: 'json',

        success: function(data) {

            $('select.multiselect').empty();

            $('select.multiselect').append(

                    $('<option></option>')

                    .text('alle')

                    .val('alle')

                    );



            $.each(data, function(index, html) {

                $('select.multiselect').append(

                        $('<option></option>')

                        .text(html.name)

                        .val(html.name)

                        );

            });



            $('.multiselect').multiselect('rebuild')

        },

        error: function(error) {

            console.log(Error:);

            console.log(error);

        }

    });

With firebug I can see that the list is generated but on select won't show up