# File lib/mail/version_specific/ruby_1_8.rb, line 55
    def Ruby18.b_value_encode(str, encoding)
      # Ruby 1.8 requires an encoding to work
      raise ArgumentError, "Must supply an encoding" if encoding.nil?
      encoding = encoding.to_s.upcase.gsub('_', '-')
      [Encodings::Base64.encode(str), encoding]
    end