[UNET] Spawn existing network GameObjects on newly connected client

I'm trying to do what the title says.

Let's say I have started the game. Have some clients connected and some networked objects spawned. All's going good. Then a new client joins. He got his new player GameObject and the ownership, but all networked objects that have existed before that new client joined doesn't spawn on the new client. Why? How can I achieve this? NetworkServer.SpawnObjects() doesn't help.

Thanks.