PVsyst 6, arguably the most popular PV modeling software in the industry, includes a temperature coefficient for the ideality factor in the single-diode model for PV modules. Multi-temperature and multi-irradiance I-V data from IEC 61853-1 tests on silicon modules, however, reveal no significant temperature dependence of the ideality factor. The series resistance shows a stronger temperature dependence, but this behavior is currently not captured by the PVsyst 6 module performance model. It is shown that, once the temperature dependence of the series resistance is included, the single-diode model can reproduce I-V curve point values Voc, Imp, and Vmp with greater accuracy.