The temperature dependence of the conductivity of amorphous hydrogenated silicon in planar and sandwich configurations prepared under identical conditions is measured. The planar conductivity is measured on heat-dried samples; the sandwich conductivity is obtained from (i) the ohmic series resistance of forward-biased Schottky diodes and (ii) the ohmic conductivity of n⁺/n/n⁺ structures. We find that the conductivities for the two configurations compare favourably, thus ruling out any appreciable effect of space charge layers on the conductivity of the planar samples.