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