We investigate the effect of the inhomogeneity of the background distribution on dynamical friction. We find a generalised Coulomb logarithm with position dependent maximum impact parameter scaling with the local scale length, which is usually much smaller than the distance to the centre of the background system. We apply the new formula to N-body calculations of satellite galaxies in Dark Matter haloes and find a systematic improvement of the orbit fits. Additionally a first order force not parallel to the motion of the massive object appears, which can be neglected at least in spherical systems due to the lack of a secular effect.