Riemann Sum Integral sensor data lost after 2021.11 update

Configuration
1

I’m not sure where to even begin this. Not sure if it’s caused by the update or if it is expected behavior.

I log my energy consumption data via MQTT every 10 seconds. The data is then added to the Riemann Sum Integral sensor and is then displayed in the Energy tab. I did this back in September, and just before the 2021.11 update I installed a few days ago, I could see my entire October energy consumption. However, everything up to the 2021.11 update is completely gone. Here’s my sensor:

sensor:
  - platform: integration
    source: sensor.kamstrup_power
    name: energy_spent
    unit_prefix: k
    round: 2

and to get it to show in the energy tab:

homeassistant:
  customize_glob:
    sensor.energy_spent:
      last_reset: '1970-01-01T00:00:00+00:00'
      device_class: energy
      state_class: measurement
      unit_of_measurement: kWh

I’m a bit annoyed that I lost this data, especially when I thought it was stored long-term when using that integration, but I guess it’s not. How do I make sure that Home Assistant won’t override/reset that sensor ever again? I want to keep that sensor’s data for many years (it’s literally just a number).