Abstract: The disclosure relates to an auxiliary locking drive for a motor vehicle lock, wherein the auxiliary locking drive, in the fitted state, provides an auxiliary locking drive train which has an auxiliary locking drive motor and a planetary gearing which is connected downstream of the auxiliary locking drive motor and has the following gearing elements: a sun gear, a planet gear carrier and a ring gear, wherein a first gearing element of the planetary gearing is coupled or is couplable to the auxiliary locking drive motor and a second gearing element of the planetary gearing is coupled or is couplable to the lock latch, wherein a switchable fixing device is provided, with which, for producing and releasing a drive coupling between the first gearing element and the second gearing element, the in each case third gearing element of the planetary gearing is fixable and releasable.