array of domain types

I wonder why domain types can not be used for specification of array 
element:

create domain objref as bigint;
create table foo(x objref[]);
ERROR:  type "objref[]" does not exist
create table foo(x bigint[]);
CREATE TABLE

Is there some principle problem here or it is just not implemented?

-- 
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company