dovecot - Aug 2020 - Environment variable in config

I am getting errors addressing environment variables. Are they supposed 
to work in such sections. Not really clear from this[1] page.


service health-check {
  # example health-check.
  executable = script -p /bin/health-check.sh
  inet_listener health-check {
      port = env:PORT0
  }
}

[1]
https://doc.dovecot.org/configuration_manual/config_file/config_variables/