Parameter group not working with type

[klausmeyer]

Against what the README @ master is telling us the parameter group does not allow to pass an type argument:

group :documents, type: Hash do
  requires :filename
  requires :content
end

Error:

lib/grape/validations.rb:135:in `group': wrong number of arguments (2 for 1) (ArgumentError)

Whereas it's working with optional parameter without any problems.

I'm using the source from master and ruby 2.1.1