StackDriiver - can't filter by user/system metadata labels

Good day guys,

I’m trying use Grafana 6.0.0 with Stackdriver DS. It seems like user-assigned labels are not seen by Grafana. For example, I have “service” label assigned to my VMs. In Stackdriver UI I can filter on it:

While in Grafana all I see is:

I.e. metadata.label.service is missing (together with user user-defined labels).

Am I missing something here?