The enfranchisement of foreigners is likely one of the most controversial frontiers of institutional change in developed democracies, which are experiencing an increasing number of non-citizen residents. We study the conditions under which citizens are willing to share power with non-citizens. To this end, we exploit the setting of the Swiss canton of Grisons, where municipalities are free to decide on the introduction of non-citizen voting rights at the local level (a so called opting-in regime). Consistent with the power dilution hypothesis, we find that enfranchisement is less likely when the share of resident foreigners is large. Moreover, municipalities with a large language/cultural minority are less likely to formally involve foreigners. In contrast, municipality mergers seem to act as an institutional catalyst, promoting democratic reforms. A supplementary panel analysis on electoral support for an opting-in regime in the canton of Zurich also backs the power dilution hypothesis, showing that a larger share of foreigners reduces support for an extension of voting rights.