We document a large increase in displays of national flags in Spain following the referendum on Catalan independence. We argue that this behavioral change is better explained by a change in norms than a change in people’s preferences. The Spanish flag was associated with Spain’s authoritarian past, and hence stigmatized. The process of Catalan independence gave individuals with nationalist views an incentive to publicly display them, initiating a process of norm change. Using a longitudinal dataset of flags on the façade of buildings and an original survey, we implement numerous tests supporting our argument. Instead, we find no evidence that the increase in flags is explained by an increase in nationalist sentiment among Spanish individuals. Moreover, symbol destigmatization came together with the destigmatization of the underlying source of stigma: flags ameliorated public assessments of Franco, without affecting private ones. Our findings highlight the role of social norms in affecting political behavior.