Abstract
In this addendum to Ref. [1] we show that the mismatch between the ρ - ω mixing parameter ϵρω as extracted from η' → π+π-γ and e+e- → π+π- can be resolved by including higher orders in the expansion in e2 in the description of the η' → π+π-γ decay. We repeat the analysis in this extended framework and update the numerical results accordingly.