  We investigate the coupling between the inflaton and massive vector fields.
All renormalizable couplings with shift symmetry of the inflaton are
considered. The massive vector can be decomposed into a scalar mode and a
divergence-free vector mode. We show that the former naturally interacts with
the inflaton and the latter decouples at tree level. The model in general
predicts $f_{NL}^\mathrm{equil} = \mathcal{O}(1)$, while in some regions of the
parameter space large non-Gaussianity can arise.
