Puphpet: The provider 'libvirt' could not be found, but was requested

[robme]

I can't create any new PuPHPet boxes because I get this error when running vagrant up:

The provider 'libvirt' could not be found, but was requested to back the machine 'default'. Please use a provider that exists.

I don't want to use libvirt. In the config.yaml it says chosen_provider: virtualbox. What has changed?

All my old boxes made with PuPHPet from months/years ago still run fine using VirtualBox provider. I'm using Fedora 22.

[robme]

I managed to fix it by using vagrant up --provider=virtualbox. It seems the new default provider was libvirt, regardless of what the config.yaml says, but if I force it to use VirtualBox then it works.