A method performed by a user equipment having a mobility management layer for circuit switched domain and a general packet radio service mobility management layer for packet switched domain, whereby the mobility management layer for circuit switched domain and the general packet radio service mobility management layer for packet switched domain are responsible for supervision that integrity protection has been activated in lower layers and neither receive nor send layer 3 signaling messages unless integrity protection has been activated for the respective domain, whereby the lower layers of each of the circuit switched domain and packet switched domain provide the mobility management layer or the general packet radio service mobility management layer respectively with an indication when a security mode control procedure for the circuit switched domain or packet switched domain has been processed successfully, whereby upon reception of a first security mode command from universal terrestrial radio access network after single radio voice call continuity handover with packet switched and circuit switched radio access bearers to universal terrestrial radio access network, the user equipment activates the security mode control procedure only for the circuit switched domain; and the user equipment provides, if not all core network domain identity information elements in a handover to universal terrestrial radio access network command message indicate the same core network domain and upon successful completion of the security control procedure for the circuit switched domain, to the mobility management layer for the circuit switched domain, the indication that the security mode control procedure for the packet switched domain has been processed successfully. whereby the mobility management layer for circuit switched domain and the general packet radio service mobility management layer for packet switched domain are responsible for supervision that integrity protection has been activated in lower layers and neither receive nor send layer 3 signaling messages unless integrity protection has been activated for the respective domain, whereby the lower layers of each of the circuit switched domain and packet switched domain provide the mobility management layer or the general packet radio service mobility management layer respectively with an indication when a security mode control procedure for the circuit switched domain or packet switched domain has been processed successfully, whereby upon reception of a first security mode command from universal terrestrial radio access network after single radio voice call continuity handover with packet switched and circuit switched radio access bearers to universal terrestrial radio access network, the user equipment activates the security mode control procedure only for the circuit switched domain; and the user equipment provides, if not all core network domain identity information elements in a handover to universal terrestrial radio access network command message indicate the same core network domain and upon successful completion of the security control procedure for the circuit switched domain, to the mobility management layer for the circuit switched domain, the indication that the security mode control procedure for the packet switched domain has been processed successfully.