The Schengen Information System for law enforcement, border control, and judicial cooperation in the European Union has over the years seen a considerable expansion of the amount and types of data stored and its functionalities, as well as its user base. In light of this transformation from a simple information-sharing tool to a full-blown investigative database, there has, however, been surprisingly little public debate and pushback against the growing surveillance and control capacities that the system enables. This article proposes to understand the largely uncontested evolution of the SIS through the concept of ‘creep’, i.e. the incremental, unforeseen, and/or stealthy development of a technological system beyond what it was originally introduced for. More specifically, it retraces how creep has in the case of the SIS been enabled and facilitated through (1) latent development principles, i.e. the rationale of building dormant features into a system that can be activated at a later point in time once technology has sufficiently matured and/or legal foundations have been adopted; and (2) technology monitoring and steering mechanisms, i.e. the continuous assessment of the readiness of key technologies for anticipated updates to the system as well as interventions in publicly funded research programmes.