An improved correction for distortions of the electric field in recoil-proton detectors, applied in neutron energy spectrum measurements, was developed. It utilizes a simple analytical expression for the representation of the response function for the entire interval of the electric charge, thus avoiding the previous separate treatment of the upper 20 to 30% of the charge range. The simplicity of the functional expression for the response function allowed the integral equation of the unfolding problem to be solved analytically. This refined unfolding technique apparently provides a better resolution, as it shows the spectrum deformation due to the large scattering resonances to be more pronounced. This highly accurate analytical unfolding procedure is likely to be applicable in other areas as well.