  The inert doublet model contains a neutral stable particle which is an
excellent dark matter candidate. We discuss in this paper the indirect
signatures of this model in gamma-rays when the dark matter mass is larger than
the $W$ boson mass. We show that, in addition to the featureless gamma-ray
spectrum produced in the annihilations into two weak gauge bosons, the model
generically predicts a distinctive spectral feature from the internal
bremsstrahlung process $H^0 H^0 \rightarrow W^+ W^- \gamma$. We discuss under
which conditions the spectral feature is generated and we construct a number of
benchmark points, compatible with the observed relic density and all other
direct and indirect detection experiments, which lead to a sharp gamma-ray
feature from internal bremsstrahlung.
