In the notes to Table 1, a unit conversion was incorrect. The text should read 1 MJ Gyr-1 = 6.02e+13 g s-1. As a consequence in the 3rd paragraph of Sect. 3, the mass loss taking place in τ Boo b should be dot M_X = 0.011 MJ Gyr-1 for ρ = 1 g cm-3, or dot M_X = 3.4 M⊕ Gyr-1 in Earth mass units. Independently, the values of “log F_X accumulated”, in Col. 12 of Table 1 were calculated using an obsolete formula and were thus slightly underestimated, generally by ⪉0.2. As a consequence Fig. 2 should show all values at a slightly higher position, although this is of no relevance for the conclusions of the paper. Table 1 and Fig. 2 are reproduced in their correct version here. At the end of 5th paragraph of Sect. 2, the hard limit of X-ray flux accumulated after 10 Gyr should be 1022.14 erg cm-2, instead of 1021.76 erg cm-2, and our highest flux is now 1021.23 erg cm-2 instead of 1021.05 erg cm-2. Table 1 is only available in electronic form at http://www.aanda.org