Over the last decade we have learned a great deal about the conditions that allow a conformal field theory to have an effective description in terms of semiclassical gravity. But what about when we add defects or boundaries to the CFT? Under what conditions can we expect those too to be described by gravity plus semiclassical branes? By examining Lorentzian BCFT correlators, I will argue that approximate ‘bulk brane’ singularities place restrictive constraints on the spectrum of a BCFT. These constraints are not expected to be satisfied generically and suggest that typical boundaries lead to a breakdown of semiclassical gravity.