MQTT Statestream and template sensors not working together?

Configuration
1

Greetings fellow Home Assisted people,

I have an issue trying to use MQTT statestream with a template sensor. I have a sensor (sensor.grid_active_power) and I need to have its negated value published via MQTT.

I created a template sensor:

sensor:
  - platform: template
    sensors:
      grid_power_input: 
        unique_id: "Huawei_grid_active_power_negated"
        friendly_name: "Grid Active Power Import" 
        unit_of_measurement: "W"
        device_class: power
        value_template: "{{ states('sensor.grid_active_power') | int * -1}}"

and this seems to work fine.
Then I need to publish this with a bunch of other sensors to MQTT. I used MQTT statestream:

mqtt_statestream:
  base_topic: huawei
  include:
    entities:
      - sensor.grid_voltage
      - sensor.active_power
      - sensor.grid_active_power
      - sensor.grid_power_input
      - sensor.fq489tx_battery_level
      - sensor.fq489tx_battery_autonomy
      - sensor.fq489tx_charging_remaining_time

The surprise is that all the native sensors get published but my template sensor is not.

Any idea why?

Kind regards,
Thomas