We analyse the sensitivity of the Deep Underground Neutrino Experiment (DUNE) to a sterile neutrino, combining information from both near and far detectors. We quantify often-neglected effects which may impact the event rate estimation in a 3+1 oscillation scenario. In particular, we find that taking into account the information on the neutrino production point, in contrast to assuming a point-like neutrino source, affects DUNE's sterile exclusion reach. Instead, implementing exact oscillation formulae, including a two slab density profile, does not result in any visible change in the sensitivity.