For 0 < s ≤ 1, we characterize those compact sets X with the property that each function harmonic in Ẋ and satisfying a little o Lipschitz condition of order s is the limit in the Lipschitz norm of orders of functions harmonic on neighbourhoods of X. As an application of the methods we give a spectral synthesis result in the space of locally integrable functions whose laplacian belongs to Bp(Rd), the containing Banach space of the Hardy space Hp(Rd).