  We calculate the one-loop corrections to TeV scale dark matter annihilation
in a model where the dark matter is described by an SU(2)$_L$ triplet of
Majorana fermions, such as the wino. We use this framework to determine the
high and low-scale MS-bar matching coefficients at both the dark matter and
weak boson mass scales at one loop. Part of this calculation has previously
been performed in the literature numerically; we find our analytic result
differs from the earlier work and discuss potential origins of this
disagreement. Our result is used to extend the dark matter annihilation rate to
NLL' (NLL+O($\alpha_2$) corrections) which enables a precise determination of
indirect detection signatures in present and upcoming experiments.
