Comparison of polarized flux densities from FFP8 simulations with (S_bpm) and without (S_nobpm) bandpass mismatch leakage. The difference between the polarized flux densities normalized by the uncertainty on the polarized flux density, Δ = (S_bpm−S_nobpm) /σ, is plotted against the input polarized flux density. The errors in the polarized flux density due to leakage are always subdominant with respect to the uncertainties due to the noise.