A method for preserving backward compatibility involves adding a new virtual method to a first version of a code package comprising a plurality of members to obtain a second version of the code package, wherein the plurality of members include a plurality of virtual methods having at least a first virtual method that is assigned a first token number and a second virtual method that is assigned a second token number sequentially after the first token number, converting a set of code that is part of the first version of the code package to obtain a converted file, modifying the converted file to include backward compatibility information associated with a plurality of token numbers assigned to the plurality of virtual methods in the first version of the code package, and adjusting the assigned first and second token numbers at one of linking time and runtime based on the backward compatibility information.