It has recently been proposed that the electron microscopic mobility in hydrogenated amorphous silicon is of the order of 100cm2V−1s−1, and that the observed lower mobility values result from scattering by potential fluctuations arising from defect centres which have a negative effective correlation energy. We show that such potential fluctuations cannot lower the mobility to its observed value of 10cm2V−1s−1. Moreover, we find that the experimental evidence used to support the claim of a higher mobility can be adequately explained by the lower of the accepted values.