Abstract: Sender-receiver games model signalling systems as solutions to coordination problems. I claim that sender-receiver games are minimal models of the evolution of signalling systems. They represent only difference makers for the evolution of signalling systems. I claim that these models should be robust. In general, robustness requires that a model yields the explanandum for a sufficiently wide range of initial conditions and dynamics. I will offer a more precise version of robustness that applies to sender-receiver games, as minimal models of the evolution of signalling systems.