Work occupies a central place in most people’s lives, yet a secondary one in most of political philosophy. This article attempts to show the negative theoretical consequences of this neglect by taking the example of the concept of constituent power as it appears in the writings of Emmanuel Joseph Sièyes and Karl Marx. Both authors conceived it as made up of the working classes. This, however, makes them both run into the same paradox: how to politically represent a class that (...) is characterised by a non-political activity – work? I argue that neither of them gives a satisfactory response since both rely on an implausible account of objective class interests based on fragile grounds. I conclude by showing that the political representation of workers is a theoretical and practical problem that the concept of constituent power is unable to resolve. (shrink)