Get memberships api ignores membership_type_id if contact_id is present

Not sure if this is indented functionality but I'm pretty sure it didn't work this way in 4.3.

If requesting membership information for a specific contact_id AND membership_type_id, what we get is a list of all memberships for that contact.

Example on the demo site:
/civicrm/ajax/rest?entity=Membership&action=get&debug=1&sequential=1&json=1&membership_type_id=2&contact_id=13

returns one membership for contact 13 with membership_id = 1.

If this is a bug, it's a bad one.