Gaze holds great potential for fast and intuitive hands-free user interaction. However, existing methods typically suffer from the Midas touch problem, i.e. the difficult distinction between gaze for perception and for user action; proposed solutions have required custom-tailored, application-specific user interfaces. Here, we present SPOCK, a novel gaze interaction method based on smooth pursuit eye movements requiring only minimal extensions to button-based interfaces. Upon looking at a UI element, two overlaid dynamic stimuli appear and tracking one of them triggers activation. In contrast to fixations and saccades, smooth pursuits are not only easily performed, but also easily suppressed, thus greatly reducing the Midas touch problem. We evaluated SPOCK against dwell time, the state-of-the-art gaze interaction method, in a simple target selection and a more challenging multiple-choice scenario. At higher task difficulty, unintentional target activations were reduced almost 15-fold by SPOCK, making this a promising method for gaze interaction.