API: when getting contact chaining relationships, the relationship direction is ignored

Let's say that contact 187 is the child of contact 166. If you try to get contact 187 with it's children like this:

$result = civicrm_api3('Contact', 'get', array(
'sequential' => 1,
'id' => 187,
'api.Relationship.get' => array('contact_id_b' => "\$value.id", 'relationship_type_id' => 1),
'options' => array('return' => "last_name"),
));

Then it returns the relationship with contact 166 as well, although 166 is the parent of 187, and not the child.

This issue is related to CRM-15983.