  Let K be a non-archimedean field, and let f in K(z) be a rational function of
degree d>1. If f has potentially good reduction, we give an upper bound,
depending only on d, for the minimal degree of an extension L/K such that f is
conjugate over L to a map of good reduction. In particular, if d=2 or d is
greater than the residue characteristic of K, the bound is d+1. If K is
discretely valued, we give examples to show that our bound is sharp.
