API call to delete tag with IN array fails

The following call (formed by API Explorer):
$result = civicrm_api3('Tag', 'delete', array(
'id' => array('IN' => array(8, 9)),
));

fails with:

{ "is_error":1, "error_message":"A fatal error was triggered: One of parameters (value: ) is not of the type Positive" }

Problem confirmed on the demo site.