MQTT JSON string with "0" not working

Configuration
1

Hello,

I have a MQTT Message with a JSON string inside:

{
     "0": {
         "name": "", 
         "value": 1902
      }
}

From this I want to have the “value”.
I made a mqtt sensor like this:

sensor:
  - name: "RPM Ventilation"
    state_topic: "device/message"
    value_template: "{{ value_json.0.value }}"

But I get only “unknown” in the entity and this error message in the log:

Template variable error: dict object has no element 0 when rendering '{{ value_json.0.value }}'

If I send a manual message with “test” instead of “0” everything works as expected:

MQTT message:

{
     "test": {
         "name": "", 
         "value": 1902
      }
}

Sensor:

sensor:
  - name: "RPM Ventilation"
    state_topic: "device/message"
    value_template: "{{ value_json.test.value }}"

→ Entity “RPM Ventilation” has 1902 as value.

Why is “0” so difficult to process and where is this behavior described and how I can get this working?

2 
{{ jv["0"].value }}