Uncertainties ΔC_κ(ℓ) (shaded area) in the prediction of the non-linear weak lensing spectra C_κ(ℓ) from drawing samples for Ω_m, σ₈, h, n_s and w from a Gaussian parameter likelihood, for which we use a prior on the wCDM model combining BAO, lensing and the CMB (Euclid 10-bin BAO spectra, Euclid 10-bin weak lensing spectra and Planck CMB temperature and polarization spectra). The uncertainty is compared to the ellipticity spectra |$C_E^\epsilon (\ell )$| (green line) and |$C_B^\epsilon (\ell )$| (red line) determined with the CNPT model.