Modal not working ???

It seems that use of **PushModalAsync **/ **PopModalAsync **does'nt work ???

I try showing a simple page and wait until it is dismissed by the.
According to what I have been able to find on the net, this should be quite simple:

await this.Navigation.PushModalAsync(new SubPages.Page1());
var poppedPage = (SubPages.Page1) await this.Navigation.PopModalAsync();
// Inspect data on the poppedPage

Unfortunately the **PopModalAsync **closes the form...

What am I doing wrong?