Bootstrap 4 beta自定义复选框

Question

有没有办法用.invalid-feedback显示.custom-checkbox？测试版更新后.has-danger课程不再可用。

<label class="custom-control custom-checkbox">
    <input type="checkbox" class="custom-control-input is-invalid" required>
    <span class="custom-control-indicator"></span>
    <span class="custom-control-description">Check this custom checkbox</span>
    <span class="invalid-feedback">
        <strong>Error!</strong>
   </span>
</label>

jsfiddle