* @address: A D-Bus address.
* @flags: Flags from the #GDBusServerFlags enumeration.
* @guid: A D-Bus GUID.
- * @observer: A #GDBusAuthObserver or %NULL.
+ * @observer: (allow-none): A #GDBusAuthObserver or %NULL.
* @cancellable: A #GCancellable or %NULL.
* @error: Return location for server or %NULL.
*