A procedure for changing, in particular for updating, a firmware of a head station of a modular node, having a transfer of a compatibility verification routine stored on the head station from the head station on which a first firmware is stored in a nonvolatile manner to a computer connected to the head station, a verification using the verification routine executed on the computer as to whether a second firmware is compatible with the head station, and a replacement of the first firmware on the head station by the second firmware if the verification has the result that the second firmware is compatible with the head station, and also a suitably equipped head station.