[syslog-ng] Inability to filter/log hostnames

I'm running syslog-ng 3.2.4 from RedHat's RPM. Unfortunately, I can't seem to log the hostname as specified in the incoming UDP packet. We don't do DNS resolution; rather, just want to log what the sending host is passing along. No relays in the mix, but we have keep_hostname() enabled. My global options: flush_lines(10); flush_timeout(750); time_reopen (10); log_fifo_size (1000); keep_hostname (yes); When I log $HOSTNAME or $HOST, I just get the sender's IP address. Similarly, filters based on these macros don't work properly. This all seemed to work on prior versions of syslog-ng (2.something). Any ideas? Thanks! Norman