AddRoutersLabels with Prometheus does not work

Traefik Traefik v2
1

Hello.
I am trying to enable prometheus metrics.
But when I enable AddRoutersLabels, I get startup error:

command traefik error: field not found, node: addRoutersLabels

Is it a bug, or I miss something? Traefik version is 2.4.14.

My config:

metrics:
  prometheus:
    addEntryPointsLabels: true
    addRoutersLabels: true
    entryPoint: metrics
    buckets:
      - 0.1
      - 0.3
      - 1.2
      - 5.0
2

It looks like this is the PR that added the flag and it was merged in Traefik 2.5: Add router metrics by jorge07 · Pull Request #7510 · traefik/traefik · GitHub

It would be good to be able to browse the docs for a particular version though as I had the same issue and I'd have probably spotted it earlier if I could select my own Traefik version