```ruby
Vagrant.configure('2') do |config|
  if Vagrant.has_plugin?("vagrant-berkshelf") then
    config.berkshelf.enabled = false
  end
end
```

Fix double quotes vs single quotes.
user
```ruby
Vagrant.configure('2') do |config|
  if Vagrant.has_plugin?('vagrant-berkshelf') then
    config.berkshelf.enabled = false
  end
end
```
assistant