paperclip content-type detection for Office

content_type_detector.rb

module Paperclip
  module ContentTypeDetectorOverrides
    def calculated_type_matches
      possible_types.select do |content_type|
        if content_type.start_with?('application/vnd.openxmlformats-officedocument')
          content_type == type_from_file_contents ||
            type_from_file_contents == 'application/zip'
        else
          content_type == type_from_file_contents
        end
      end
    end
  end

  class ContentTypeDetector
    prepend ContentTypeDetectorOverrides
  end
end