Sinatra::Application.environment に staging が追加できない

Sinatra::Application.environment に staging が追加できなくてもやもやしてたら

NG

require 'sinatra/base'
require 'sinatra/config_file'

class MyApp < Sinatra::Base

  set :root, File.dirname(__FILE__)
  set :environments, %w{development test production staging}

  register Sinatra::ConfigFile
  config_file 'path/to/config.yml'

  get '/' do
    settings.hello
  end

end

OK

require 'sinatra/base'
require 'sinatra/config_file'

class MyApp < Sinatra::Base

  register Sinatra::ConfigFile

  set :root, File.dirname(__FILE__)
  set :environments, %w{development test production staging}

  config_file 'path/to/config.yml'

  get '/' do
    settings.hello
  end

end

orz
うそやん......

ちなみに、NGのほうをそのまま実行すると

undefined method `hello' for MyApp:Class (NoMethodError)

的なエラーメッセージになります。。