Nautilus Unable to Preview GIMP Files with Hidden Background

[Chris Spencer <gmane 20 evilspam spamgourmet com>]

I've noticed that Nautilus doesn't create a preview for GIMP xcf files 
if you hide the background layer. It doesn't seem to mind if any other 
layers are hidden or not, but if the background layer is hidden then 
Nautilus won't display a thumbnail. Has anyone else noticed this? Is 
there a reason for this behavior, or should I submit a bug report?

Chris