postgres_exporter crashes on startup on database with 4kb block_size

I have pmm-agent running on PostgreSQL 12.5 database compiled with 4kb block_size. Agent can't collect postgres metrics because postgres_exporter crashes on startup with the following error:

^[[36mINFO^[[0m[2021-04-22T11:23:50.604+03:00] panic: unknown unit for runtime variable: "4kB"  ^[[36magentID^[[0m=/agent_id/7a38a68d-955e-4f5d-9c74-f65b2abbd42d ^[[36mcomponent^[[0m=agent-process ^[[36mtype^[[0m=postgres_exporter

It seems that 4kB unit size does not exist in https://github.com/percona/postgres_exporter/blob/master/cmd/postgres_exporter/pg_setting.go