Methods and devices for instructing a subscriber identity module in a cellular communications network to process non-standard authentication information in a standard manner are disclosed. One embodiment of a method comprises receiving a first message authentication code (MAC) and an authentication management field (AMF) at a subscriber identity module as part of an authentication protocol, calculating a second MAC and determining whether the second MAC is equivalent to the first MAC. If the first and second MAC are not equivalent, the SIM calculates a third MAC and determines whether the first MAC is equivalent to the third MAC, and if so, the subscriber identity module processes the AMF in a predefined or standard manner.