# File lib/zip/zip.rb, line 1525
    def mkdir(entryName, permissionInt = 0755)
      if find_entry(entryName)
        raise Errno::EEXIST, "File exists - #{entryName}"
      end
      @entrySet << ZipStreamableDirectory.new(@name, entryName.to_s.ensure_end("/"), nil, permissionInt)
    end