[Serusers] Registration problem - save function

Hello everyone, I've found and issue with save function and I'd like to know what I'm doing wrong. I configured, it correctly pass the porxy authentication, and then a new record is added to the location database using the save function after receiveing a register request. The problem is when the same terminal changes the IP address (is using DHCP). The save function adds a new record to the location database, instead of updating the existing record changing the contact field. I looked at mysql log, and the update command is including the location information in the where statement, thats is why mysql is adding a new record instead of updating the existing one. Is that a problem with the save function? Should I configure something in order to make it look for just the username and domain without including the contact info? Thank you very much in advance. Best regards Hernán