  We study the stationary Josephson current in a junction between a topological
and an ordinary (topologically trivial) superconductor. Such an S-TS junction
hosts a Majorana zero mode that significantly influences the current-phase
relation. The presence of the Majorana state is intimately related with the
breaking of the time-reversal symmetry in the system. We derive a general
expression for the supercurrent for a class of short topological junctions in
terms of the normal state scattering matrix. The result is strongly asymmetric
with respect to the superconducting gaps in the ordinary ($\Delta_0$) and
topological ($\Delta_{\mathrm{top}}$) leads. We apply the general result to a
simple model of a nanowire setup with strong spin-orbit coupling in an external
magnetic field and proximity-induced superconductivity. The system shows
parametrically strong suppression of the critical current $I_c \propto
\Delta_{\mathrm{top}}/R_N^2$ in the tunneling limit ($R_N$ is the normal state
resistance). This is in strong contrast with the Ambegaokar-Baratoff relation
applicable to junctions with preserved time-reversal symmetry. We also consider
the case of a generic junction with a random scattering matrix and obtain a
more conventional scaling law $I_c \propto \Delta_{\mathrm{top}}/R_N$.
