  The Syst\`eme Internationale d'unit\'es (SI system) is about to undergo its
biggest change in half a century by redefining the units for mass and current
in terms of the fundamental constants h and e, respectively. This change
crucially relies on the exactness of the relationships which link these
constants to measurable quantities. Here we directly compare the integer
quantum Hall effect in epitaxial graphene with that in GaAs/AlGaAs
heterostructures. We find no difference of the quantized resistance value
within the relative standard uncertainty of our measurement of 8.6\times10-11,
being the most stringent test of the universality of the quantum Hall effect in
terms of material independence.
