Encoding bug in ripper with heredoc strings

ripper_bug.rb

require 'ripper'
require 'pp'
sexp = Ripper.sexp(DATA.read)
pp sexp
sexp = sexp.flatten
heredoc = sexp[sexp.flatten.index(:@tstring_content) + 1]
string = sexp[sexp.flatten.rindex(:@tstring_content) + 1]
puts
puts "String:  #{string.inspect} Encoding: #{string.encoding.inspect}"
puts "Heredoc: #{heredoc.inspect} Encoding: #{heredoc.encoding.inspect}"

__END__
# encoding: utf-8

<<-eos
ƒøø
eos
"ƒøø"

ripper_bug_output.txt

$ ruby -v ripper_bug.rb
ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin11.0.0]
[:program,
 [[:string_literal,
   [:string_content,
    [:@tstring_content, "\xC6\x92\xC3\xB8\xC3\xB8\n", [4, 0]]]],
  [:string_literal, [:string_content, [:@tstring_content, "ƒøø", [6, 1]]]]]]

String:  "ƒøø" Encoding: #<Encoding:UTF-8>
Heredoc: "\xC6\x92\xC3\xB8\xC3\xB8\n" Encoding: #<Encoding:ASCII-8BIT>