Bootstrap-select issue

Bootstrap-select doesn't play nicely with the jQuery Validation plugin. When the select element is left empty, the "error" class is properly added, but when the select element becomes valid (non-empty value), the "error" class is not removed, apparently because the 'onchange' event is fired programmatically.

HTML

<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
<link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.6.4/css/bootstrap-select.min.css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.6.4/js/bootstrap-select.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.13.1/jquery.validate.min.js"></script>
<h3>Bootstrap-select</h3>
<form id="testform">
    <select name="testselect" class="selectpicker">
        <option value="">--Select--</option>
        <option value="a">A</option>
        <option value="b">B</option>
        <option value="c">C</option>
    </select>
    <button type="submit" class="btn btn-primary">Submit</button>
</form>

JavaScript

$('#testform').validate({
    ignore: ':hidden:not(.selectpicker)',
    rules: {
        testselect: 'required'
    },
    submitHandler: function(form) {
        alert('Form submitted!');
    }
});