  The search for sharp features in the gamma-ray spectrum is a promising
approach to identify a signal from dark matter annihilations over the
astrophysical backgrounds. In this paper we investigate the generation of
gamma-ray lines and internal bremsstrahlung signals in a toy model where the
dark matter particle is a real scalar that couples to a lepton and an exotic
fermion via a Yukawa coupling. We show that the Fermi-LAT and H.E.S.S. searches
for line-like spectral features severely constrain regions of the parameter
space where the scalar dark matter is thermally produced. Finally, we also
discuss the complementarity of the searches for sharp spectral features with
other indirect dark matter searches, as well as with direct and collider
searches.
