UNION and array types

UNIONs don't appear to work when you are trying to union 2 tables that
include array types.
Example:
create table foo (bar int8[]);
insert into foo (bar) values ('{1,2,3}');
select * from foo union select * from foo;
ERROR: Unable to identify an ordering operator '<' for type 'bigint[]'
Use an explicit ordering operator or modify the query

Is it possible to make this work? Please tell me yes. :)

eric