One problem in the origins of life is how parasitic side-reactions can be mitigated. It is known that spatial self-organisation can help with this, making autocatalytic chemical systems more robust to invasion by parasitic species. In previous work we have shown that in such scenarios parasitic reactions can actually be beneficial. Here we demonstrate for the first time a system in which the presence of a parasitic autocatalytic cycle is not only beneficial but actually necessary for the persistence of its host. This occurs due to the effect the parasite has on the spatial organisation of the system; the host-parasite system is more stable than the host alone, despite the fact that the parasite’s direct effect on its host is purely negative. We briefly discuss the implications for the origins of life.