The shutdown problem is the problem of programming an agent so that it behaves useful during normal operation and facilitates a shutdown if and only if the creator wants to shut the agent down. First, we revisit a formalisation of this problem from the literature and we show that solutions are essentially unique. Second, we formally define ad-hoc constructions. Last, we present one trivial ad-hoc construction for the shutdown problem and show that every solution to the shutdown problem must come from an ad-hoc construction, which is to be expected given the uniqueness from the first point. We relate this to non-existence theorems from the literature.