[ERROR] when using generic list with RPC

I'm trying to use the RPC to call a method that expects a generic List (List<int>), calling the PRC via PhotonView I get the following error:

Exception: cannot serialize(): System.Collections.Generic.List`1[System.Int32]
at ExitGames.Client.Photon.Protocol.Serialize (System.IO.MemoryStream dout, System.Object serObject, Boolean setType) [0x00000] in <filename unknown>:0
at ExitGames.Client.Photon.Protocol.SerializeObjectArray (System.IO.MemoryStream dout, System.Object[] objects, Boolean setType) [0x00000] in <filename unknown>:0

If I use a generic dictionary I do not get any errors...