The present paper deals with the accuracy of wavefront curvature restoration based on pit displacement measurements in a Talbot wavefront sensor under Gaussian illumination conditions. The measurement possibilities of the Talbot wavefront sensor are theoretically investigated. A theoretical model based on the Fresnel regime is used to determine the intensity distribution in the near field, and the effect of the Gaussian field is described in terms of the spatial spectrum of the grating image. The effect of wavefront curvature on the measurement error of the Talbot sensor is discussed-particularly, the measurement of wavefront curvature is investigated.