  The annihilation of TeV-scale leptophilic dark matter into electron-positron
pairs (hereafter $e^+e^-$) will produce a sharp cutoff in the local cosmic-ray
$e^+e^-$ spectrum at an energy matching the dark matter mass. At these high
energies, $e^+e^-$ cool quickly due to synchrotron interactions with magnetic
fields and inverse-Compton scattering with the interstellar radiation field.
These energy losses are typically modelled as a continuous process. However,
inverse-Compton scattering is a stochastic energy-loss process where
interactions are rare but catastrophic. We show that when inverse-Compton
scattering is modelled as a stochastic process, the expected $e^+e^-$ flux from
dark matter annihilation is about a factor of $\sim$2 larger near the dark
matter mass than in the continuous model. This greatly enhances the
detectability of heavy dark matter annihilating to $e^+e^-$ final states.
