Class methods using 'extend self' do not get published

[gnilrets]

The documentation for B.cool does not show up unless I remove extend self and use def self.cool

module A
  # Public: These are my module B methods.
  module B
    extend self

    # Public: Class method that does something really cool.
    #
    # Returns cool
    def cool
      "Cool beans"
    end
  end
end