почему я получаю неинициализированную константу Devise name Error при запуске сервера webrick?

В моем приложении я использовал ruby 1.9.2 и rails 3.0.3 и также установил Devise gem.Проблема начинается, когда я запускаю сервер Webrick я получаю неинициализированную константу Devise name Error.

       /home/app/Workspace/project/Library_Management/Library_Management/config/initializers/devise.rb:3:in `<top (required)>': uninitialized constant Devise (NameError)
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/engine.rb:201:in `block (2 levels) in <class:Engine>'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/engine.rb:200:in `each'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/engine.rb:200:in `block in <class:Engine>'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/initializable.rb:25:in `instance_exec'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/initializable.rb:25:in `run'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/initializable.rb:50:in `block in run_initializers'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/initializable.rb:49:in `each'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/initializable.rb:49:in `run_initializers'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/application.rb:134:in `initialize!'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/application.rb:77:in `method_missing'
from /home/app/Workspace/project/Library_Management/Library_Management/config/environment.rb:5:in `<top (required)>'
from /home/app/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:54:in `require'
from /home/app/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:54:in `require'
from /home/app/Workspace/project/Library_Management/Library_Management/config.ru:3:in `block in <main>'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/builder.rb:46:in `instance_eval'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/builder.rb:46:in `initialize'
from /home/app/Workspace/project/Library_Management/Library_Management/config.ru:1:in `new'
from /home/app/Workspace/project/Library_Management/Library_Management/config.ru:1:in `<main>'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/builder.rb:35:in `eval'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/builder.rb:35:in `parse_file'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/server.rb:162:in `app'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/server.rb:253:in `wrapped_app'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.2.3/lib/rack/server.rb:204:in `start'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands/server.rb:65:in `start'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands.rb:30:in `block in <top (required)>'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands.rb:27:in `tap'
from /home/app/.rvm/gems/ruby-1.9.2-p180/gems/railties-3.0.9/lib/rails/commands.rb:27:in `<top (required)>'
from /home/app/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:58:in `require'
from /home/app/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:58:in `rescue in require'
from /home/app/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:35:in `require'

Спасибо