When I try to cleanup my rails versions with sudo gem cleanup rails

I get the following error:

Cleaning up installed gems...
Attempting to uninstall rails-2.3.5
Unable to uninstall rails-2.3.5:
Gem::InstallError: cannot uninstall, check `gem list -d rails`
Attempting to uninstall rails-1.2.6
Unable to uninstall rails-1.2.6:
Gem::InstallError: cannot uninstall, check `gem list -d rails`

gem list -d rails results in:

rails (2.3.8, 2.3.5, 1.2.6)
  Author: David Heinemeier Hansson
  Rubyforge: http://rubyforge.org/projects/rails
  Homepage: http://www.rubyonrails.org
  Installed at (2.3.8): /Library/Ruby/Gems/1.8
               (2.3.5): /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8
               (1.2.6): /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8

  Web-application framework with template engine, control-flow layer,
  and ORM.

Any one know what's wrong?