Error message hide in smart-select

This Code:

Summary
<f7-list-item title="customer" smart-select :smart-select-params="{openIn: 'popup', searchbar: true, searchbarPlaceholder: 'select customer'}">
                <select name="car" v-model="customerId" validate required
....

‘item-input-error-message’ is hidden when validate as required.

What should I do, please?