The democratic legitimation imperative of the modern state has been conceptualised as the barrier that stops the environmental state from developing into a green or eco-state - and thus as the glass ceiling to a socio-ecological transformation of capitalist consumer democracies. Here, I suggest that this state-theoretical explanation of the glass ceiling needs to be supplemented by an analysis of why democratic norms and procedures, which had once been regarded as essential for any socio-ecological transformation, suddenly appear as one of its main obstacles. I conceptualise the new eco-political dysfunctionality of democracy as one dimension of a more encompassing legitimation crisis of democracy which, in turn, has triggered a profound transformation of democracy. Ultimately, exactly this transformation constitutes the glass ceiling to the socio-ecological restructuring of capitalist consumer societies. It changes democracy into a tool for the politics of unsustainability, in which the legitimation-dependent state is a key actor.