This invention relates to a method for negotiating at least one parameter of a protocol that is operated between a first protocol entity (1) and a second protocol entity (2), comprising receiving (301) a first negotiation message (3) that carries a first value for the at least one parameter, wherein the first value is an invalid value for the at least one parameter, and sending (309) a second negotiation message that carries a second value for the at least one parameter in response to the first negotiation message (3). The invention further relates to a computer program, a computer program product, a system (30) a terminal (10) and a network element (20). The protocol may for instance be a Radio Link Protocol, and the first (3) and second (4) negotiation messages may for instance be eXchange Identification XID command and response, respectively.