closed stream (IOError) on Raspberry Pi

[shokai]

/home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:65:in `close': closed stream (IOError)
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:65:in `close'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:31:in `initialize'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:58:in `call'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:58:in `sleep'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:58:in `initialize'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:56:in `loop'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/arduino.rb:56:in `initialize'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/main.rb:14:in `new'
        from /home/sho/src/ruby/arduino_firmata/lib/arduino_firmata/main.rb:14:in `connect'
        from samples/led_blink.rb:6