image upload with active admin and refile

Question

I am using Active admin as my rails application backend.
I want to make an image upload on the admin panel with refile uploader.
Active admin depends on formtastic form builder, so I added "refile-input" gem which integrates refile with formtastic:

Gemfile:
# Backend
gem 'activeadmin', github: 'activeadmin'
gem "refile-input", require: ["inputs/refile_input"]
#image uploads
gem "refile", require: "refile/rails", github: 'refile/refile'
gem "refile-mini_magick"
gem "refile-s3"

After successfully building the form for Cover model, I submitted an image and got this error:

IOError in Admin::CoversController#create
closed stream

lambda do |*args, &block|
    target = self.__getobj__
    target.__send__(mid, *args, &block)
  end
end

Any thoughts on how to approach this problem?

10x!