pg_basebackup streaming issue from standby

Hi,

I've just tried using pg_basebackup to take a backup of a standby with
"-x stream" but it never finishes.  This is what I get:

thom@swift:~/Development$ pg_basebackup -p 5489 -D data3 -x stream -Pv
xlog start point: 0/6000020
pg_basebackup: starting background WAL receiver
78020/78020 kB (100%), 1/1 tablespace
xlog end point: 0/6F819F8
pg_basebackup: waiting for background process to finish streaming...


pg_stat_replication on the standby looks like this:

thom@test=# select * from pg_stat_replication ;
-[ RECORD 1 ]----+------------------------------
pid              | 29161
usesysid         | 10
usename          | thom
application_name | pg_basebackup
client_addr      |
client_hostname  |
client_port      | -1
backend_start    | 2012-03-08 01:33:32.799491+00
state            | startup
sent_location    | 0/0
write_location   |
flush_location   |
replay_location  |
sync_priority    | 0
sync_state       | async
-[ RECORD 2 ]----+------------------------------
pid              | 29162
usesysid         | 10
usename          | thom
application_name | pg_basebackup
client_addr      |
client_hostname  |
client_port      | -1
backend_start    | 2012-03-08 01:33:32.921461+00
state            | streaming
sent_location    | 0/6F819F8
write_location   |
flush_location   |
replay_location  |
sync_priority    | 0
sync_state       | async


It gets stuck here and never finishes.  This also prevents the standby
from shutting down unless pg_basebackup is terminated.  I've attached
the log from the standby in case it's of any use (with
log_min_messages set to debug5).

This is using an unpatched copy of latest Git master.

--
Thom