  We show that the monopole scalar charge of black holes in
Einstein--Maxwell--dilaton theory is proportional to the electric potential at
the event horizon, with a proportionality factor given by (minus) the scalar
coupling constant. We also show that the scalar charge, in the weak electric
charge limit, does not depend on the black hole spin. This result can be very
useful to circumvent spin degeneracy issues when testing the theory against
gravitational waves observations.
