Get affected rows after Delete (mysql)

I can't seem to get reliable results after deleting a row(s) using mysqli.  The afftect_rows is always 0.  

I'm using php5.2 and the mysqli method

Something like this:

$sql = "
				DELETE FROM classRoster WHERE id=123
			";
			if ($result = $this->mysqli->query($sql)) {
				return $this->mysqli->affected_rows;   ///ALWAYS RETURNS 0
			}else{
				//log error
			}		

I have confirmed that the row is in fact deleted, but still get 0 as affected_rows.   Please help!