API version overriding version parameter in body

Hello there fine fellows!

Beginning to use and love Grape, but have run into a serious issue which I am unable to resolve myself.

I have an endpoint described as such:

    params do
      optional :description, :type => String,  :desc => 'Book description'
      optional :reference,   :type => String,  :desc => 'Book reference'
      requires :version,     :type => Integer, :desc => 'Book current version'
    end

This works fine with API versioning via headers when I pass in this body:

    {"description":"Updated Description","reference":"b:a","version":2}

However, when I use API versioning via path, the version parameter is set to the API version from the path, which results in a 403 with this body:

    {"error":"invalid parameter: version"}

I verified this at coerce.rb by adding these lines after line 14:

    puts attr_name
    puts params[attr_name]

This produces:

    version
    pacioli

where pacioli is my API version from:

    class App < ::Grape::API
      version 'pacioli', :using => :path

I believe this to be 100% incorrect. :-)

Let me know if I can help in any way!

P.S. The 403 is weird in itself as line 15 of coerce.rb certainly appears to throw a 400.