[Rails 3.2.8] ActiveSupport::BufferedLogger extension, undefined_method

[Erwin]

I tried to extend it , with this class , loaded at config time :

  config.autoload_paths += Dir["#{config.root}/lib", "#{config.root}/lib/**/", "#{config.root}/app/inputs"]

lib/extension.rb

class ActiveSupport::BufferedLogger

  def detailed_error(e)

    error(e.message)

    e.backtrace.each{|line| error line }

  end

end

but calling it in my controller 

rescue ActiveRecord::RecordInvalid

   logger.detailed_error($!)

raises an error =>   undefined method `detailed_error' for #<Logger:0x007fb8ecaabcc8>

what's wrong with my class definition ?

thanks for feedback