simple rep does not show material in drawing BOM

I have a part of which I would like to add a simple rep (with less features) in the drawing. I relate the BOM to this simple rep, but the material all of a sudden does not appear in the BOM anymore. It still shows up when I relate the BOM to the master rep.

If I compare model properties of the master rep and the simple rep, one value changes but I cant figure out where to change this value. Does anyone know whats going on?

see images: