  We compute the O(1/M,m_s) heavy quark and SU(3) corrections to B_s -> D_s e
nu form factors. In the limit of vanishing light quark mass, B_s -> D_s e nu
form factors are given in terms of the the B -> D e nu form factors, the
leading order chiral parameter g, and two O(1/M) chiral parameters $g_1$ and
$g_2$. All the chiral parameters can be extracted, in principle, from other
heavy meson decays. Analytic counterterms proportional to the strange quark
mass are presented for completeness, but no predictive power remains when they
are included. Anomalously large loop corrections warn of poor convergence of
the heavy quark chiral symmetry expansion for these processes. This suggests
that naive extrapolations of B \to D form factors relying on heavy quark and
chiral symmetries, as often used in monte carlo simulations of lattice QCD, may
incur large errors.
