  We investigate the decay mechanisms in the Ds+ --> omega pi+ and Ds+ --> rho0
pi+ transitions. The naive factorization ansatz predicts vanishing amplitude
for the Ds+ --> omega pi+ decay, while the Ds+ --> rho0 pi+ decay amplitude
does have an annihilation contribution also in this limit. Both decays can
proceed through intermediate states of hidden strangeness, e.g. K, K*, which we
estimate in this paper. These contributions can explain the experimental value
for the Ds+ --> omega pi+ decay rate, which no longer can be viewed as a clean
signature of the annihilation decay of Ds+. The combination of the \pi(1300)
pole dominated annihilation contribution and the internal K, K* exchange can
saturate present experimental upper bound on Ds+ --> rho0 pi+ decay rate, which
is therefore expected to be within the experimental reach. Finally, the
proposed mechanism of hidden strangeness FSI constitutes only a small
correction to the Cabibbo allowed decay rates Ds--> K K*, phi pi, which are
well described already in the factorization approximation.
