Prometheus metrics and unknown values

Hello,
I decided to try exporting haas metrics to prometheus. It works fine, however I noticed some issue. I have a sensor which reports data randomly (issues with bluetooth range). So sometimes sensor is giving unknown value in haas UI, but in prometheus metrics it reports 0. This messes the charts as I have 0 instead of nulls. Is there a way to report unknown metrics values as nulls for prometheus?

I use latest haas 0.109.6