We experimentally study the role of punishment for cooperation in dynamic public-good problems where past payoffs determine present contribution capabilities. The beneficial role of punishment possibilities for cooperation is fragile: successful cooperation hinges on the presence of a common understanding of how punishment should be used. If high-contributors punish too readily, the group likely gets on a wasteful path of punishment and retaliation. If punishment is administered more patiently, even initially uncooperative groups thrive. Hence, when today’s punishment also determines tomorrow’s cooperation abilities, it seems crucial that groups agree on the right ‘dose’ of sanctions for punishment to support cooperation.