Laravel carbon get current month in dutch

I'm trying to show the full current month name in dutch. I've tried it like this:

\Carbon\Carbon::now()->subMonth()->format('F')

But then I see July so not what I want. My app service provider looks like this:

public function boot()
{
    Carbon::setLocale('nl');
}

Any Idea what I could do to get this to work?

(diffForHumans is working correctly)