Ruby-on-Rails：ActiveAdmin SuperClass Mismatch TypeError

http://net.tutsplus.com/tutorials/ruby/create-beautiful-administration-interfaces-with-active-admin/

但是当我到rails生成active_admin：install时

我明白了：

$rails generate active_admin:install
/home/user/active_admin/config/application.rb:13:in `<module:ActiveAdmin>': superclass mismatch for class Application (TypeError)
from /home/user/active_admin/config/application.rb:12:in `<top (required)>'
from /home/user/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.13/lib/rails/commands.rb:24:in `require'
from /home/user/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.13/lib/rails/commands.rb:24:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

似乎无法找到有这个问题的其他人.我甚至删除了active_admin并从头开始重新开始整个事情……没有骰子.