Backdrop for stack modal

I want to add a backdrop to my stacked modal, like here:

and put this:

ion-modal.stack-modal { 
 --box-shadow: 0 28px 48px rgba(0, 0, 0, 0.4); 
 --backdrop-opacity: var(--ion-backdrop-opacity, 0.32);

in my global.scss.

Now I’m opening my Modal with:

const modal = await this.modalCtrl.create({
      component: StackedModalPage,
      cssClass: 'stack-modal',
      componentProps: {

Should it work this way? It’s not working for me.

I tried it also in the page.scss file and everything I found elsewhere, but a smaller modal over a bigger modal still get no backdrop.
No one here with the same problem?