When democracy is under attack, the hope is often that citizens will punish undemocratic incumbents. However, recent studies show that not all citizens punish governments for their undemocratic actions. In this article, we argue that citizens' understanding of and satisfaction with democracy are sources of heterogeneous reactions. In a survey experiment conducted in Germany and Poland, we show that the importance that citizens attach to specific institutions under threat, as well as their understanding of democracy, can explain much of the variance in citizens' responses to undemocratic actions. Citizens are willing to defend what they consider important for democracy – regardless of whether this reflects theoretical conceptions of democracy. Moreover, in times of democratic backsliding, Polish ‘critical citizens’, those who are dissatisfied with the way democracy works in Poland, are more likely to punish governments for undemocratic actions. Our findings help us understand how to increase citizens' resilience against democratic backsliding.