  We present measurements of a combination of the decay constants of the light
pseudoscalar mesons and the gradient flow scale $t_0$, which allow to set the
scale of the lattices generated by CLS with $2 + 1$ flavors of
non-perturbatively improved Wilson fermions. Mistunings of the quark masses are
corrected for by measuring the derivatives of observables with respect to the
bare quark masses.
