PHP пишет ошибку при вызове bind_param() mysqli

Можете подсказать решение

Ошибка Warning: mysqli_stmt::bind_param(): Number of elements in type definition string doesn't match number of bind variables in

          $query = "INSERT INTO `messages_api` (`id`, `username`, `displayname`, `message_date`, `message_type`, `message_status`, `source`, `message`, `item_title`, `item_url`,`message_id` , `item_id` , `recipient_id`) VALUES (NULL, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
          $stmt = $con->prepare($query);
          $stmt->bind_param($username, $displayname, $message_date, $message_type, $message_status, $source, $message_content, $item_title, $item_url, $message_id, $item_id, $recipient_id);
          $stmt->execute();