Setting rectangle-preview face in init.

[Ergus]

Hi:

I am trying to set the rectangle-preview face in my init.el (to set it
different to region) but I get an error that rectangle-preview is not
a valid face. I see it is not documented, but it is supposed to be
customizable in the customize dialog.

What I am missing here??

Is it possible that rect.el is loaded lazily, so when the init.el is
executed it has not been loaded yet?