Error: Platform systemmonitor does not generate unique IDs. ID disk_free already exists

I’m getting an error on every start as listed below. But, I still do have a sensor.disk_free sensor that does work fine and is apparently having a unique id because it can be edited.

The old systemmonitor portion in my configuration.yaml has been edited out. I can’t understand what this error is about, any ideas?

Logger: homeassistant.components.sensor
Source: helpers/entity_platform.py:610
Integration: Sensor (documentation, issues)
First occurred: 20:55:01 (1 occurrences)
Last logged: 20:55:01

Platform systemmonitor does not generate unique IDs. ID disk_free already exists - ignoring sensor.disk_free

Will be fixed in the next release.

Awesome. Thanks!