Location of RE 0503−289 in the log T_eff–log g diagram (the ellipse indicates the error range) compared with evolutionary tracks for post-AGB stars that experienced a very late thermal pulse (Althaus et al. 2009). These are labeled with the respective stellar masses (in M_⊙). Positions of hydrogen-deficient PG 1159-type stars and DO-type WDs are indicated by squares and circles, respectively.