is 8.4 array_agg() supposed to work with array values?

Hi,

The docs at http://developer.postgresql.org/pgdocs/postgres/functions-aggregate.html
don't prohibit using array values with array_arg(), so I assumed that it would work.
However, with CVS HEAD from Friday afternoon, I get

test=> select version() ;
version
----------------------------------------------------------------------------------------------------------------------
PostgreSQL 8.4devel on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.1.2 20070502 (Red Hat 4.1.2-12), 64-bit
(1 row)

test=> select v.a, pg_typeof(v.a) from (values (array[1,2]), (array[3,4])) as v(a) ;
a | pg_typeof
-------+-----------
{1,2} | integer[]
{3,4} | integer[]
(2 rows)

test=> select array_agg(v.a) from (values (array[1,2]), (array[3,4])) as v(a) ;
ERROR: could not find array type for data type integer[]
test=>

If this is expected behavior, the docs should mention the restriction.

-- todd