Contact API does not return custom data

Had some code that worked in 3.1.6 but broke on upgrade to 3.2.5.

require_once 'api/v2/Contact.php';
$params = array(
'contact_id' => $contact_id,
'return_custom_51' => 1,
'return_custom_52' => 1
);
$result=civicrm_contact_get($params);

Result does not return custom data.

'return.custom_51' => 1,
'return.custom_52' => 1

notation (i.e. dot instead of underscore didn't work either.
Does not return custom data any more.