Does not contain a definition for `clientOwnedObjects'??

So Unity gives me this error when trying to retrieve the player object when he disconnects

The docs tell me that clientOwnedObjects can be found in NetworkConnection:
http://docs.unity3d.com/ScriptReference/Networking.NetworkConnection.html

This however returns an error:

Code (CSharp):

1. void OnServerDisconnect(NetworkMessage mess) {
2.    Debug.Log(mess.conn.clientOwnedObjects);
3.    NetworkServer.DestroyPlayersForConnection(mess.conn);
4. }

And I get this error:

I use Unity 5.1.2f1 Personal

I simply want to retrieve the player object before destroying it so the server can save some data...
Can anyone help please?

Thanks