  Assuming the existence of a new real scalar singlet $s^0$ coupled to the
Standard Model via a scalar quartic portal interaction, we compute the
radiative corrections to the decay rates of the heavy scalar mass eigenstate to
a couple of gauge bosons $ZZ$ and $W^+W^-(\gamma)$, showing that they can give
a contribution as large as ${\cal{O}}$(5\%) and ${\cal{O}}$(7\%), respectively.
We also explicitly analyze in detail their dependence on the heavy mass $m_S$
and on the scalar mixing angle $\alpha$, finding that, especially in the
large-mass region, these depend on the sign of $\sin\alpha$.
