AJAX validation for Html::active...() fields

I’m using ActiveForm for my model form. However, for a couple of fields, instead of using


$form->field()->dropDownList()

where


$form = ActiveForm::begin();

to display the field, I use


Html::activeDropDownList($model, 'attribute')

and for the corresponding model attribute, I have a validation rule (inside the model). I’ve also enabled enableAjaxValidation and enableClientValidation in the form. I notice that while the AJAX validation is triggered for all fields created with the


$form->field()

method, my custom Html::activeDropDownList() fields do not trigger the validation. How am I going to automatically trigger the AJAX validation for these fields too?