For dual connectivity with a UE where a master radio access node communicates using one of an older or newer radio access technology (RAT) and a secondary radio access node communicates using the other of the older or newer RAT, the master node a) sends to the secondary node an addition request message comprising configuration information enabling the secondary node to operate with the master node for dual connectivity with a user equipment (UE); b) receives from the secondary node in reply a request acknowledgement message acknowledging participation by the secondary node in the dual connectivity; and thereafter c) participates in the dual connectivity when communicating wirelessly with the UE. The addition request and request acknowledgement messages are in accordance with RRC signaling of the older RAT regardless which of the older and the newer RAT the master node uses when participating in the dual connectivity.