  The octet-singlet mixing angle $\theta_P$ in the pseudoscalar meson nonet is
deduced from the rich set of accurate data on $J/\psi$ decays into a vector and
a pseudoscalar meson. Corrections due to non-ideal $\omega$-$\phi$ mixing have
been included for the first time and turn out to be crucial to find $\theta_P =
-16.9 \pm 1.7$ degrees, which is appreciably less negative than previous
results coming from similar analyses.
