tcp_keepalive values not taking

Postgresql 8.2.4
FreeBSD 6.2

According to
http://www.postgresql.org/docs/current/static/runtime-config-connection.html
the tcp_keepaliave variables take the OS setting if 0, or use whatever value
one puts in postgresql.conf.

I tried the following values in postgresql.conf:

tcp_keepalives_idle = 600               # TCP_KEEPIDLE, in seconds;
                                        # 0 selects the system default
tcp_keepalives_interval = 60            # TCP_KEEPINTVL, in seconds;
                                        # 0 selects the system default
tcp_keepalives_count = 10               # TCP_KEEPCNT;
                                        # 0 selects the system default

Yet when I do "show tcp_keepalives_idle", "show tcp_keepalives_interval" or
"tcp_keepalives_count" they all show zero. Tried both reload and
restart.

Also tried changing sysctl net.inet.tcp.keepidle=600 in FreeBSD. It still
doesn't show in postgresql.

Any suggestions?