Research on early false belief understanding has entirely relied on affect-neutral measures such as judgments (standard tasks), attentional allocation (looking duration, preferential looking, anticipatory looking), or active intervention. We used a novel, affective measure to test whether preschoolers affectively anticipate another's misguided acts. In two experiments, 3-year-olds showed more expressions of suspense (by, e.g. brow furrowing or lip biting) when they saw an agent approach a scene with a false as opposed to a true belief (Experiment 1) or ignorance (Experiment 2). This shows that the children anticipated the agent's surprise and disappointment when encountering reality. The findings suggest that early implicit knowledge of false beliefs includes anticipations of the affective implications of erring. This vital dimension of beliefs should no longer be ignored in research on early theory of mind.