is it bug? - printing boolean domains in sql/xml function

Hello

related to http://www.postgresql.org/message-id/CAFj8pRDTAVfNrAzwEt+ewMfRBDZFfVa8W17Kk_E12fb6T-ZNXQ@mail.gmail.com

boolean domains is serialised to string different than boolean

postgres=# CREATE DOMAIN booldomain as bool;
CREATE DOMAIN

-- fully expected behave
postgres=# select true, true::booldomain;
bool | booldomain
------+------------
t | t
(1 row)

postgres=# select true::text, true::booldomain::text;
text | text
------+------
true | true
(1 row)

-- unexpected behave
postgres=# select xmlforest(true as bool, true::booldomain as booldomain);
xmlforest
---------------------------------------------
<bool>true</bool><booldomain>t</booldomain>
(1 row)

is it expected behave?

Regards

Pavel