klass_sym = klass.to_s.to_sym
            missing_styles[klass_sym] ||= Hash.new
            missing_styles[klass_sym][attachment_name.to_sym] ||= Array.new
            missing_styles[klass_sym][attachment_name.to_sym].concat(missed.to_a)
            missing_styles[klass_sym][attachment_name.to_sym].map!(&:to_s).sort!.map!(&:to_sym).uniq!