Enthalpies of formation and mixing of binary solid and liquid magnesium alloys have been calculated by application of the Miedema model and compared with data reported in literature. The Miedema model has originally been developed for alloys containing at least one transition metal. The model parameters have been developed over the years and became fixed around the end of the nineteen eighties. In the present paper, the validity of the model is investigated for all binary Mg-alloy systems, also including alloys without a transition metal. The much larger number of literature data, that is presently available, allows for a more precise estimation of one of the model parameters associated with Mg and to adapted calculations for binaries of Mg with transition metals. In addition, an extension of the model to binaries of Mg with non-transition metals is introduced. For these alloys an additional negative contribution to the heat of formation and mixing is added.@en