Using the built light.X10 (hassio on a raspberry pi)

As per documentation I added the lines of configuration for X10 to configuration.yaml, checked the config with the web interfaced and restarted my Rpi but the device did not show up.

configuration.yaml:

light:
 platform: x10
 devices:
  id: a13
  name: Tuin verlichting

After looking around for clues I found this in the log:

Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/homeassistant/helpers/entity_platform.py", line 82, in async_setup
    SLOW_SETUP_MAX_WAIT, loop=hass.loop)
  File "/usr/lib/python3.6/asyncio/tasks.py", line 358, in wait_for
    return fut.result()
  File "/usr/lib/python3.6/asyncio/futures.py", line 245, in result
    raise self._exception
  File "/usr/lib/python3.6/concurrent/futures/thread.py", line 56, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/lib/python3.6/site-packages/homeassistant/components/light/x10.py", line 45, in setup_platform
    x10_command('info')
  File "/usr/lib/python3.6/site-packages/homeassistant/components/light/x10.py", line 33, in x10_command
    return check_output(['heyu'] + command.split(' '), stderr=STDOUT)
  File "/usr/lib/python3.6/subprocess.py", line 336, in check_output
    **kwargs).stdout
  File "/usr/lib/python3.6/subprocess.py", line 403, in run
    with Popen(*popenargs, **kwargs) as process:
  File "/usr/lib/python3.6/subprocess.py", line 709, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.6/subprocess.py", line 1344, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'heyu': 'heyu'

So did I do something wrong? Are the instruction for X10 incomplete?