new post above - reverse order

[SteanlyCZ]

Hi, I need to sort (in wagtail administration) by sort_order but to sort from largest to smallest

if i add:
sort_order_field = 'sort_order'
contributions are sorted from smallest to largest (and the new contribution is at the bottom)

I need the sorting reversed, so that the new post is at the top...

sort_order_field = '-sort_order' not working