Save/open-Dialog, file order, directories first

The file-open/save dialog can be sorted alphabetically by clicking on the column header or by manipulating ~/.config/gtk-2.0/gtkfilechooser.ini as described in the answers here and here.

However, I'd like to have the subdirectories sorted on top, i.e. directories a/ b/ c/ before files a.txt b.png c.svg and so on. Is there a way to do it?

I'm using Xubuntu 15.10.