Recent findings indicate that individuals use prosocial options as default in social dilemmas and specifically first order public goods. In two studies, we test whether this spontaneous cooperation effect generalizes to second order public goods in the form of punishment behavior in one-shot and iterated public goods, and investigate the underlying motivations. In line with spontaneous cooperation, quick punishment is larger than slow punishment. Negative affect moderates this spontaneous punishment effect in one-shot public goods, in that punishment decisions are more quickly taken by persons that are more upset about the contribution behavior of their group members. Unlike spontaneous cooperation, spontaneous punishment is not driven by dispositional prosociality, but by situational high contributions. A significant three-way interaction in an overall-analysis indicates that the spontaneous punishment effect is mainly driven by above-average, highly upset contributors.