Unlisten / listen in a transaction failure

I came across some unusual behavior with listen. Basically, if you
unlisten and listen inside of a transaction, new notices are not
picked up right away - but they will show up if you send yourself
a notice. It also works as expected if you unlisten, commit, and
then re-listen. Tested on 9.1 and 9.2. Demo psql script:

listen abc; \t
\! psql -p 5491 -c 'notify abc'
select * from pg_listening_channels();

begin; unlisten *; listen abc; commit;
\! psql -p 5491 -c 'notify abc'
select * from pg_listening_channels();

notify abc;

Output of above on 9.1 with psql -e:

listen abc;
LISTEN
Showing only tuples.
NOTIFY
select * from pg_listening_channels();
abc

Asynchronous notification "abc" received from server process with PID 10879.

begin;
BEGIN
unlisten *;
UNLISTEN
listen abc;
LISTEN
commit;
COMMIT
NOTIFY
select * from pg_listening_channels();
abc

notify abc;
NOTIFY
Asynchronous notification "abc" received from server process with PID 10882.
Asynchronous notification "abc" received from server process with PID 10876.

--
Greg Sabino Mullane greg(at)endpoint(dot)com
End Point Corporation
PGP Key: 0x14964AC8