We study the effects of the vicinity between a shallow donor nucleus and an I1-type basal stacking fault (BSF) in GaN. We propose a numerical calculation, in the “effective potential” formalism, of energies and envelope functions of electrons submitted to the conjunction of attractive potentials caused by the BSF and the donor. We show that the donor localizes the electron along the plane of the BSF, even when the donor lies as far as 10 nm from the BSF. Conversely, the presence of the BSF enhances the donor binding energy by up to a factor of 1.8, when the donor is placed exactly on the BSF. We briefly discuss the probability of occurrence of such a situation in, e.g., a-plane GaN, as well as its consequences on transport and optical properties of this material.