error

mcantor@cottlebook ~/src/ext/rails/guides (master): bundle exec redcarpet --version
Redcarpet 3.1.2

mcantor@cottlebook ~/src/ext/rails/guides (master): bundle exec rake guides:generate:html
/Users/mcantor/.rbenv/versions/2.1.0/bin/ruby rails_guides.rb
Generating active_model_basics.md as active_model_basics.html
/Users/mcantor/src/ext/rails/guides/rails_guides/markdown/renderer.rb:18:in `header': wrong number of arguments (2 for 3) (ArgumentError)
        from /Users/mcantor/src/ext/rails/guides/rails_guides/markdown.rb:76:in `render'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/markdown.rb:76:in `generate_header'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/markdown.rb:20:in `render'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:205:in `block in generate_guide'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:195:in `open'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:195:in `generate_guide'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:144:in `block in generate_guides'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:142:in `each'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:142:in `generate_guides'
        from /Users/mcantor/src/ext/rails/guides/rails_guides/generator.rb:97:in `generate'
        from rails_guides.rb:63:in `<main>'
rake aborted!
Command failed with status (1): [/Users/mcantor/.rbenv/versions/2.1.0/bin/r...]
/Users/mcantor/src/ext/rails/guides/Rakefile:11:in `block (3 levels) in <top (required)>'
Tasks: TOP => guides:generate:html
(See full trace by running task with --trace)