sslcompression / PGSSLCOMPRESSION not behaving as documented?

I'm having a hard time getting SSL compression working (or even figuring
out why it's not working) with my local Postgres server. The setting [1] is
documented to default to on, but according to the banner when I connect
with psql, it's off. It's still off even if I explicitly set
PGSSLCOMPRESSION=1:

maciek(at)gamera:~$ PGSSLCOMPRESSION=1 psql -h localhost
psql (9.4.0, server 9.2.9)
SSL connection (protocol: TLSv1.2, cipher: DHE-RSA-AES256-GCM-SHA384, bits:
256, compression: off)
Type "help" for help.

Nothing interesting in the logs. As far as I can tell, my OpenSSL version
is recent enough to support this:

maciek(at)gamera:~$ ldd /usr/lib/postgresql/9.2/bin/postgres | grep ssl
libssl.so.1.0.0 => /lib/x86_64-linux-gnu/libssl.so.1.0.0
(0x00007f144a25d000)

(is that the right way to check?)

I'm running this on Ubuntu 14.04 with PGDG Postgres packages. Any ideas?

Thanks,
Maciek

[1]: http://www.postgresql.org/docs/9.2/static/libpq-envars.html