Listen queue overflow with default config on FreeBSD

[pooltechniker]

Setting up a basic web server on FreeBSD using the default configuration gives me this error in /var/log/messages on each request to httpd:

sonewconn: pcb 0xffffa00002ce3000 (0.0.0.0:443 (proto 6)): Listen queue overflow: 1 already in queue awaiting a
cceptance (4 occurrences), euid 0, rgid 0, jail 0

Using the default configuration, netstat -aL shows:

# netstat -aL | grep http
#

There are no listen queues for HTTP nor HTTPS, even though the man page says: "The backlog option is 10 by default", but it seems - at least on FreeBSD - that's not true.
After adding tcp backlog 128 to obhttpd.conf, netstat shows queues for both HTTP and HTTPS:

# netstat -aL | grep http
tcp4  0/0/128                          *.https                
tcp6  0/0/128                          *.https                
tcp4  0/0/128                          *.http                 
tcp6  0/0/128                          *.http

And no more Listen queue overflow messages are shown.