Drawing on empirical evidence from online citizen feedback on the 2012 Egyptian Constitution, we demonstrate that despite normative skepticism about implications of participatory constitution making, citizen participation matters. Using data of more than 650,000 online votes and comments on the constitution, we find that draft provisions with higher public approval are less likely to change and those with lower approval are more likely to change. We also find that Articles related to rights and freedoms are more likely to change based on online public input. Finally, following the boycott of the Constituent Assembly by non-Islamists, changes in draft Articles based on public feedback drop sharply. These findings highlight the conditions under which participatory constitution making becomes more effective. First, consensus among citizens over the most salient issues increases the probability that those issues would be successfully incorporated in the constitution. Second, without ex ante elite agreement over the design of the constitution, it becomes difficult to account for citizen proposals amid political clash between elites.