When around humans, one might expect that a social robot would act according to the social norms people expect of each other. When someone does not adhere to a prevalent social norm, people usually feel threatened and uncomfortable. In comparison, insight is needed into what is perceived as socially normative behavior for robots. We conducted an experiment in which a robot approached a participant in order to determine the effect of personal space invasion. We manipulated the agent-type (human/robot) and the approach speed (slow/fast) of the agent towards the participant. Unexpectedly, our results show that the participants displayed more compensatory behavior toward the robot than toward the human confederate. Interestingly, we found that participants tended to trust the faster robot more compared and the faster human less. We consider these responses toward personal space invasion as an indication that people react differently to robots as they do to humans, and with more intensity.