Client_auth conditional on PathPrefix

This should be a common use-case:

I'd like to authenticate a client cert, but only when the url contains a specific PathPrefix. The app behind traefik is a web-site, which also handles rpc-calls on

Client certs are only passed for rpc calls, for which they are mandatory.

In apache this is simply:

<LocationMatch "^/rpc">
      SSLVerifyClient require

I've attempted to achieve this by creating two routers with different TLS options:

      - "traefik.http.routers.whoami.rule=Host(``)"
      - "traefik.http.routers.whoami.entryPoints=https"
      - "traefik.http.routers.whoami.tls=true"

      - "traefik.http.routers.whoami-rpc.rule=Host(``) && PathPrefix(`/rpc`)"
      - "traefik.http.routers.whoami-rpc.middlewares=passtlsclientcert@file"
      - "traefik.http.routers.whoami-rpc.entryPoints=https"
      - "traefik.http.routers.whoami-rpc.tls=true"
      - "traefik.http.routers.whoami-rpc.tls.options=rpc-options@file"

However this results in Errors: found different TLS options for routers on the same host, so using the default TLS options instead

How should this be handled?