In a recent paper [Scientific Reports 7, 8058 (2017)], Álvaro Díaz-Fernández et al. have proposed a general mechanism that enables the fine-tuning of the Fermi velocity in Dirac materials in a readily accessible way for experiments. By embedding the sample in a uniform electric field, the Fermi velocity is substantially modified. They first proved this result analytically, for the surface states of a topological insulator/semiconductor interface, and postulated its universality to other Dirac materials. Then they checked its correctness in carbon-based Dirac materials, namely graphene nanoribbons and nanotubes, thus showing the validity of their hypothesis in both continuum and tight-binding calculations and in different Dirac systems.