ERROR: invalid option "use_remote_estimate"

I test the postgresql_fdw extension,every thing is fine but when I add the
remote estimate option I get a error:

postgres=# alter foreign table test options (add use_remote_estimate
'true');
ERROR: invalid option "*use_remote_estimate*"
HINT: Valid options in this context are: schema_name, table_name, *
use_remote_explain*

regards,
--
Jov
blog: http:amutu.com/blog <http://amutu.com/blog>