'duplicate listener' on port 465

Hi,

When configuring SMTPS as described on https://doc.dovecot.org/main/core/config/submission.html#smtps, Dovecot says there is a 'duplicate listener'.

MRE:

root@dovecot24-test:/etc/dovecot/conf.d# doveconf -n
# 2.4.1-4+debian12 (7d8c0e5759): /etc/dovecot/dovecot.conf
# Pigeonhole version 2.4.1-4+debian12 (0a86619f)
# OS: Linux 6.1.0-29-amd64 x86_64 Debian 12.11
# Hostname: dovecot24-test.cyberfusion.nl
# 4 default setting changes since version 2.4.0
dovecot_config_version = 2.4.0
dovecot_storage_version = 2.4.0
protocols = submission
service submission-login {
   inet_listener submission_465 {
     port = 465
   }
}
doveconf: Error: duplicate listener: 465:*
doveconf: Fatal: Error in configuration file /etc/dovecot/dovecot.conf: 
duplicate listener: 465:*

Can anyone help me understand why this listener would be 'duplicate'? This setup worked on 2.3.21.1.

Thanks!

William David Edwards