Combined HERA data on charm production in deep-inelastic scattering have previously been used to determine the charm-quark running mass in the renormalisation scheme. Here, the same data are used as a function of the photon virtuality to evaluate the charm-quark running mass at different scales to one-loop order, in the context of a next-to-leading order QCD analysis. The scale dependence of the mass is found to be consistent with QCD expectations
