Changing forking mode is only available for private repository !

In the Administration tab, I would change forking mode from "Allow only private forks" to "Allow forks".
But it was not possible until I check "This is a private repository"

I think that the condition is reversed.

Workaround: check "private repo", change the forking mode and then uncheck "private". The forking mode is saved.

For public repository, the widgets are: see unchecked.png

After checking the "private repo" box: see checked.png