rake db:migrate gives a uninitialized class variable @@configuration in Rails error

uninitialized cl开发者_运维知识库ass variable @@configuration in Rails
/usr/lib/ruby/gems/1.8/gems/rails-2.1.0/lib/initializer.rb:19:in `configuration'
/usr/lib/ruby/gems/1.8/gems/thoughtbot-factory_girl-1.2.2/lib/factory_girl.rb:24
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'

This is the initial part of the enviroment.rb:

RAILS_GEM_VERSION = '2.1.0' unless defined? RAILS_GEM_VERSION

require File.join(File.dirname(__FILE__), 'boot')

Rails::Initializer.run do |config|

  config.gem "oauth", :version => "0.2.7", :lib => "oauth"

Is factory_girl 1.2.2 compatible with Rails 2.1? Try with a newer version of Rails. Try without factory_girl.