Yeah. There was a problem, that 4.9 did not compile on FreeBSD 15 under some circumstances, so it was skipped. 4.10.0 also failed for us, so we released 4.10.1 to make sure that FreeBSD 15 also works. You can compile 4.9 using instructions from my blog: https://www.syslog-ng.com/community/b/blog/posts/installing-syslog-ng-4-9-0-on-freebsd My suspicion is that it's something between 4.8 and 4.9, which was a huge jump.