Impact of erroneous phasing of individual spectra on the T_eff labels for the Cepheid RS Pup: top panel: MJD of the observation for individual spectra. Second panel: our individual radial velocity measurements (circles that are color-coded by MJD, cf., upper panel) versus radial velocity data used for the IRSB analysis (blue crosses, Storm et al. 2004). Spectra rephased to match the radial velocity curve are shown as pale brown squares. Using the same color coding, the third and fourth panels display the T_eff variation, and the T_eff offset between original labels and their corrected value after rephasing, respectively.