https://bugs.winehq.org/show_bug.cgi?id=50905
--- Comment #8 from Alexandre Julliard julliard@winehq.org --- This is now done through a WINEBOOTSTRAPMODE environment variable. It's set when running wineboot, but it can also be set manually if necessary. This should solve the issue with old prefixes. It's still possible to break a prefix by removing core dlls, but hopefully this will make it easier to recover.