Help with RailRoad

When I run this code I don't hace any problem: railroad -a -i -o full_models.dot -C

But if run this code: railroad -a -i -o full_models.dot -M I get this: /Users/juan/Desktop/dticket_4_03_08/vendor/rails/activerecord/lib/active_record/base.rb:1532:in `method_missing_without_paginate': undefined method `_' for #<Class:0x251965c> (NoMethodError)   from /Users/juan/Desktop/dticket_4_03_08/vendor/plugins/will_paginate/lib/will_paginate/finder.rb:93:in `method_missing'   from ./app/models/setting.rb:4   from /opt/local/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'   from /opt/local/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:27:in `require'   from /Users/juan/Desktop/dticket_4_03_08/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:496:in `require'   from /Users/juan/Desktop/dticket_4_03_08/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in'   from /Users/juan/Desktop/dticket_4_03_08/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:496:in `require'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/lib/railroad/models_diagram.rb:36:in `load_classes'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/lib/railroad/models_diagram.rb:36:in `each'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/lib/railroad/models_diagram.rb:36:in `load_classes'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/lib/railroad/app_diagram.rb:21:in `initialize'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/lib/railroad/models_diagram.rb:14:in `initialize'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/bin/railroad:31:in `new'   from /opt/local/lib/ruby/gems/1.8/gems/railroad-0.4.0/bin/railroad:31   from /opt/local/bin/railroad:16:in `load'   from /opt/local/bin/railroad:16