Unobtrusively validating using a 'required' rule or manually validating the select input using $.validate does not work as the plugin hides the raw select element, so jquery validate ignores it by default.

Fixed using the below code, would be helpful to notify users of this or include this somewhere in the plugin as an enhancement:

var $form = $("#myForm");
var validator = $form.data('validator');
validator.settings.ignore = ':hidden:not(".multiselect")';