A radio network node (RNN) (202) and a method therein, for handling of changing primary cell from a first cell (204) to a second cell (206) during re-selection of primary cell of a user equipment (UE) (208). The RNN is configured to serve the first cell, the UE is located within the first cell and is served by the RNN, and RNN and the UE are comprised in a communications system (200). The RNN transmits an RRCConnectionReconfiguration signal to the UE, which signal comprises an indication that the UE does not need to perform a random access procedure for the second cell when changing primary cell from the first cell to the second cell.