Single table inheritance - type field breaks `load_instance` when cached

[shosanna]

I noticed that if I am using a type column in my object and I want to cache it, I run into unexpected problems. I believe the reason lies in activity.rb

  # stores the correct class
  hash = {'id' => object.id, 'type' => object.class.name}

  if fields = definition.send(type)[class_sym].try(:[],:cache)
    fields.each do |field|
      raise Errors::InvalidField.new(field) unless object.respond_to?(field)
      # here it gets overriten by STI "type" field
      hash[field.to_s] = object.send(field)
    end
  end
  write_attribute(type, hash)
end

Where the type is rewritten by the one from the model's attributes and the load_instance is than throwing an error because it could not find an object based on this type. Note that this only happens if the type column is being cached.