Using syslog-ng-3.8.1-2.3.x86_64 on Leap 42.2 I get these repeated warnings in
/var/log/warn:

Jul 24 08:00:12 vandy syslog-ng[3194]: WARNING: Default value changed for the
prefix() option of systemd-journal source in syslog-ng 3.8; old_value='',
new_value='.journald.'
Jul 25 08:00:06 vandy syslog-ng[3194]: WARNING: Default value changed for the
prefix() option of systemd-journal source in syslog-ng 3.8; old_value='',
new_value='.journald.'
Jul 26 08:00:05 vandy syslog-ng[3194]: WARNING: Default value changed for the
prefix() option of systemd-journal source in syslog-ng 3.8; old_value='',
new_value='.journald.'
Jul 27 08:00:07 vandy syslog-ng[3194]: WARNING: Default value changed for the
prefix() option of systemd-journal source in syslog-ng 3.8; old_value='',
new_value='.journald.'
Jul 28 08:00:01 vandy syslog-ng[3217]: WARNING: Default value changed for the
prefix() option of systemd-journal source in syslog-ng 3.8; old_value='',
new_value='.journald.'

Bug ID	1051214
Summary	Repeated warnings from syslog-ng: Default value changed for the prefix() option of systemd-journal source
Classification	openSUSE
Product	openSUSE Distribution
Version	Leap 42.2
Hardware	Other
OS	Other
Status	NEW
Severity	Normal
Priority	P5 - None
Component	Basesystem
Assignee	bnc-team-screening@forge.provo.novell.com
Reporter	archie.cobbs@gmail.com
QA Contact	qa-bugs@suse.de
Found By	---
Blocker	---