Configure Stiebel Eltron Heatpump - write_register not working

Hi all,
I’m trying to add my Stiebel Eltron Heatpump. This is how I configured it:

modbus:
  name: stiebel_isg 
  type: tcp
  host: wp.s19d 
  port: 502

  sensors:
    name: Outside temperature
    unique_id: wp_temperature_outside
    slave: 1
    address: 506
    input_type: input
    unit_of_measurement: °C
    device_class: temperature
    scale: 0.1
    precision: 1

stiebel_eltron:
  name: wp_stiebel
  hub: stiebel_isg

Modbus reads seem to work in general - I get the outside temperature.
But for the Stiebel integration I can see the following error in the logs.

  File "/usr/src/homeassistant/homeassistant/components/climate/__init__.py", line 1029, in async_service_temperature_set
    await entity.async_set_temperature(**kwargs)
  File "/usr/src/homeassistant/homeassistant/components/climate/__init__.py", line 742, in async_set_temperature
    await self.hass.async_add_executor_job(
  File "/usr/local/lib/python3.12/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/src/homeassistant/homeassistant/components/stiebel_eltron/climate.py", line 182, in set_temperature
    self._ste_data.api.set_target_temp(target_temperature)
  File "/usr/local/lib/python3.12/site-packages/pystiebeleltron/pystiebeleltron.py", line 283, in set_target_temp
    self._conn.write_register(
    ^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'ModbusHub' object has no attribute 'write_register'

Does anyone has an idea what I am missing here?

Thanks!