No fc-match for serif, sans-serif, mono with only liberation-fonts

[Yanko Kaneti <yaneti declera com>]

Hi

Rawhide. With installed only liberation-fonts, I was surprised to see
fc-match not returning anything for "serif", "sans-serif", "mono".

Is that a bug? (I think it should be).
If it is, where?  fontconfig? liberation-fonts ?

Yanko