Embodiments of the invention relate to a technique for updating a device comprising a first and second applets implementing application code. The technique may include determining that the application code needs to be updated, generating a verification value, and sending the verification value and updated code for a function in the first applet. The updated code for the function can be stored in the second applet instead of the first applet, and the function maps of the applets can be updated to reflect the address of the updated function. The updated code can then be executed using the updated function maps to perform a process.