A method in an IP multimedia subsystem, IMS, of a telecommunications network. The loss of a secure association between a P-CSCF of the IMS and a user equipment, UE, served by the P-CSCF is detected, or a UE is relocated from a further P-CSCF to the first mentioned P-CSCF. The first mentioned P-CSCF sends a reregistration request to the UE; receives a SIP REGISTER message from the UE; and performs P-CSCF registration with the UE including establishing a new secure association with the UE.