Change opacity of component ionic-backdrop

[SergioSGil]

hi guys, anyone know how it is possible to change the opacity of an ion-backdrop is displayed behind the alert? I have tried several ways but don’t get it

Y try with

ion-backdrop {
--ion-backdrop-color: rgba(0, 0, 0, .9);
}

But opacity do not change

[SergioSGil]

Finally i’ve do it using the cssClass property in alertController

  async alertError(message: string) {
    const alert = await this.alertController.create({
      cssClass: 'alertClass',
      animated: true,
      header: 'Error',
      message,
      buttons: ['OK']
    });
    await alert.present();
  }

 ion-alert {
   &.alertClass{
     background: rgb(0,0,0,.8);
   }
 }

[SergioSGil]