Plane curves and p-adic roots of unity

We prove the following result: Let f(x, y) be a polynomial of degree d in two variables whose coefficents are integers in an unramified extension of Qp. Assume that the reduction of f modulo p is irreducible of degree d and not a binomial. Assume also that p > d2 + 2. Then the number of solutions of the inequality |f(ζ1, ζ2)| < p−1, with ζ1, ζ2 roots of unity in Q̄p or zero, is at most pd2.