An unbiased approach to correct X-ray response non-uniformity in microstrip detectors has been developed based on the statistical estimation that the scattering intensity at a fixed angle from an object is expected to be constant within the Poisson noise. Raw scattering data of SiO₂ glass measured by a microstrip detector module was found to show an accuracy of 12σ_PN at an intensity of 10⁶ photons, where σ_PN is the standard deviation according to the Poisson noise. The conventional flat-field calibration has failed in correcting the data, whereas the alternative approach used in this article successfully improved the accuracy from 12σ_PN to 2σ_PN. This approach was applied to total-scattering data measured by a gapless 15-modular detector system. The quality of the data is evaluated in terms of the Bragg reflections of Si powder, the diffuse scattering of SiO₂ glass, and the atomic pair distribution function of TiO₂ nanoparticles and Ni powder.