Multiple email receivers in prometheus alertmanager "to" field

For prometheus 1.8 I am using two "to" configurations in the same receiver.

receivers:

  - name: 'bla1-and-bla2-mails'
    email_configs:
    - to: '[email protected]' 
      from: '[email protected]'
      require_tls: false
      send_resolved: true
    - to: '[email protected]'
      from: '[email protected]'
      require_tls: false
      send_resolved: true

You can put comma separated email addresses in the to field.

to: '[email protected], [email protected]'