In this paper we present an in-situ neutron diffraction experiment on the dehydrogenation of Mg2FeH6. Stoichiometric mixtures of 2Mg + Fe were ball milled in a hydrogen environment. After desorption, the samples were exposed to different combinations of hydrogen/deuterium at different temperatures in order to absorb hydrogen or deuterium at specific synthesis steps. Using this hydrogen/deuterium absorption mixture, we found that there may be a hydrogen-deuterium exchange happening when both Mg2FeH6 and MgD2 are present. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.