Unable to create correct Mongoid model from JSON

Question

I'm trying to create a Mongoid model from the corresponding JSON structure.

However it does not include the embedded relation frameworks. I'm using Mongoid 4.0. Am I doing something wrong or is this a bug?

If I store any embedded relation via store_as under a different name than the default serialization, it works as expected. Also, if I create the model in the database from JSON rather than initialize it everything's fine...

JSON input

{
  "name": "MyName",
  "frameworks": [
    {
      "name": "grails",
      "runtime": "groovy",
      "versions": []
    }
  ]
}

Models

require 'mongoid'

class Vendor
  include Mongoid::Document
    include Mongoid::Attributes::Dynamic

  # fields
  field :name, type: String
  # relations
  embeds_many :frameworks
  # validations
  validates :name, presence: true
  validates :frameworks, presence: true
end

class Framework
  include Mongoid::Document

  embedded_in :vendor

  field :name, type: String
  field :runtime, type: String
  field :versions, type: Array
  # validations
  validates :name, presence: true
  validates :runtime, presence: true
end

Test App

require 'json'
require 'require_relative'
require_relative 'vendor'

begin
  json = JSON.parse(File.read('input.json'))
  @profile = Vendor.new(json)
  puts @profile.inspect
rescue JSON::ParserError => e
  puts "Error: " << e.to_s
end