PStore File Encoding Issue

pstore_file_test.rb

require 'pstore'

# Some code (like Rails) sets this so that strings are represented in Unicode
Encoding.default_internal = 'UTF-8'

# But if we do that, PStore randomly blows up
begin
  print "Trying to store some values with PStore"
  store = PStore.new('test.pstore')
  (1..1000).each do |i|
    store.transaction {
      store["Key#{i}"] = "value #{i}"
      print '.'
    }
  end
  puts "Success!"
rescue => err
  puts "O NOES! Received error: #{err.to_s}"
end

# Why is that?
file = File.open("file_test", File::CREAT | File::RDWR | File::BINARY) do |f|
  puts "Using IO Constants, File Encoding: #{f.external_encoding.to_s}"
  # UTF-8? But...I told Ruby this was a BINARY file...what's going on?
end

# But if I do it this way
file = File.open("file_test", "w+b") do |f|
  puts "Using String mode, File Encoding: #{f.external_encoding.to_s}"
  # Yeah, ASCII-8BIT - that's more like it
end

# So if we monkey-patch PStore thusly:
class PStore
  def open_and_lock_file(filename, read_only)
    if read_only
      begin
        file = File.new(filename, 'rb')
        begin
          file.flock(File::LOCK_SH)
          return file
        rescue
          file.close
          raise
        end
      rescue Errno::ENOENT
        return nil
      end
    else
      file = File.new(filename, 'w+b')
      file.flock(File::LOCK_EX)
      return file
    end
  end
end

# And if we try our little PStore test again:
begin
  print "Trying to store some values with PStore"
  store = PStore.new('test2.pstore')
  (1..1000).each do |i|
    store.transaction {
      store["Key#{i}"] = "value #{i}"
      print '.'
    }
  end
  puts "Success!"
rescue => err
  puts "O NOES! Received error: #{err.to_s}"
end

# Everything works!