Results of a test designed to assess the accuracy of the atmospheric parameters inferred from hot subdwarf spectra polluted by a cooler main sequence star. The left panel shows the apparent values of T_eff and log g inferred from a series of polluted model spectra by fitting the same hot subdwarf spectra as used for the observational data, while the right panel highlights the effect of the pollution on the derived value of log N(He) /N(H)). The tracks connect models with the same input values for the hot subdwarf component, but different levels of pollution as arising from a main sequence star (assumed to be at the same distance as the EHB star) with T_eff = 3000, 3500, 4000, 4500, 4750, 5000, 5250, 5500, 5750, 6000, 6250, 6500, 6750, 7000 and 7250 K (with log g = 4.5 fixed). The solid (dotted) tracks refer to a hot subdwarf component with log g = 6.0 (5.8) and T_eff = 50 000, 42 000, 34 000, and 26 000 K (from left to right). For the coolest main sequence component the atmospheric parameters inferred are very close to the input values for the hot subdwarf model, but they become more and more unreliable as the main sequence star becomes hotter and has a larger impact on the spectrum.