After upgrade pg_dumpall fails

Spent yesterday upgrading to 7.2.1, wasn't a walk in the park but it's
working.

Last night my system ran a pg_dumpall and displayed an error:

--
-- pg_dumpall (7.2.1)
--
\connect template1
DELETE FROM pg_shadow WHERE usesysid <> (SELECT datdba FROM pg_database
WHERE datname = 'template0');

connected to template1...
ERROR: Unable to convert abstime 'invalid' to timestamptz

The error seems to come from pg_dumpall at the following line:

$PSQL -d template1 -At -c "\
SELECT
'CREATE USER \"' || usename || '\" WITH SYSID ' || usesysid
|| CASE WHEN passwd IS NOT NULL THEN ' PASSWORD ''' || passwd || '''' else
'' end
|| CASE WHEN usecreatedb THEN ' CREATEDB'::text ELSE ' NOCREATEDB' END
|| CASE WHEN usesuper THEN ' CREATEUSER'::text ELSE ' NOCREATEUSER' END
|| CASE WHEN valuntil IS NOT NULL THEN ' VALID UNTIL '''::text
|| CAST(valuntil AS TIMESTAMP) || '''' ELSE '' END || ';'
FROM pg_shadow
WHERE usesysid <> (SELECT datdba FROM pg_database WHERE datname =
'template0');" \

Looking at pg_shadow the structure looks like:

# \d pg_shadow
Table "pg_shadow"
Column | Type | Modifiers
-------------+---------+-----------
usename | name |
usesysid | integer |
usecreatedb | boolean |
usetrace | boolean |
usesuper | boolean |
usecatupd | boolean |
passwd | text |
valuntil | abstime |
Unique keys: pg_shadow_usename_index,
pg_shadow_usesysid_index
Triggers: pg_sync_pg_pwd

Is valuntil's type improper? Anything else that might cause this?