Missing required on material select

[e-belair]

I can't make material dropdown select working with required attribute It seems not appearing on the library

[nshahan]

Are you using the angular_forms package? https://webdev.dartlang.org/api?package=angular_forms

[e-belair]

I guess, this is the code of the form:

<form (ngSubmit)="onSubmit()" #etablissementSearchForm="ngForm" *ngIf="searching == true">
                <material-dropdown-select
                        buttonText="{{etablissementSearch.zone??'Toutes zones'}}"
                        deselectLabel="Toutes zones"
                        [(ngModel)]="etablissementSearch.zone"
                        [options]="zonesByZonage"
                        [required]="true"
                        class="block-width dropdown-align-with-text">
                </material-dropdown-select>
</form>

Also, I've searched for the required attr in the angular_component/material_select lib but I did not found nothing.