According to the Principle of Alternative Possibilities, a person is morally responsible for something s/he has done only if s/he could have done otherwise. Frankfurt cases are designed to show that this principle is false. Many Frankfurt cases feature a sign that alerts a counterfactual intervener, of what the agent is going to decide and do. Problems with these cases have led some authors to design examples with no such sign, and where the counterfactual factor is replaced by a mechanism that actually blocks alternative possibilities. In this paper, it is argued that these cases are not successful, for they violate a plausible condition on moral responsibility that Fischer has called 'reasons-responsiveness'. Según el Principio de Posibil...