Exclude logging certain connections?

Hi,

is there a way to exclude certain connections, for example recurring monitoring connections, from the postgres.log?

I found this from in old post on stackexchange.com:

postgres=# create role mon login;
CREATE ROLE
postgres=# alter role mon set log_connections=off;
ERROR:  parameter "log_connections" cannot be set after connection start

(source:
https://dba.stackexchange.com/questions/118018/is-it-possible-to-exclude-specific-users-in-log-activity-of-postgresql)

There is no connection at the time. So why do I get the error? And what can I do about it?

Cheers,
Paul