We study whether the arrival of a new immigrant wave changes natives' acceptance of former immigrants and their descendants. We exploit the 2015 European refugee crisis and the context of German open-list local council elections where voting for immigrant-origin candidates represents a consequential revealed preference. We combine hand-collected candidate-level election data with administrative asylum seeker data. Continuous difference-in-differences estimations (based on municipal %∆ in asylum seekers) reveal that immigrant-origin candidates receive more votes the more asylum seekers arrived locally. This shift in social group boundaries is driven by candidates with a Southern/Eastern European origin being culturally similar to Germans.