Parameter values of the best-fitting PEMD model for the lens galaxy SDSS J0252+0039 inferred based on the U-band (F390W) imaging, in comparison to the I-band (F814W) reconstruction by Vegetti et al. (2014). The optimized parameters are the lens strength b, the position angle θ (with respect to the original telescope rotation), the axis ratio q, the (three-dimensional) mass-density slope γ, the external shear strength Γ and its position angle Γ_θ. In both bands, the reconstruction was carried out using the adaptive gradient source regularization and casting back each pixel (n = 1). The typical statistical errors of our U-band reconstruction are of the order 10⁻¹ for the angles and 10⁻³ for the remaining parameters.