  The potential sensitivity to isospin-breaking effects makes LHC searches for
mono-W signatures promising probes of the coupling structure between the
Standard Model and dark matter. It has been shown, however, that the strong
sensitivity of the mono-W channel to the relative magnitude and sign of the
up-type and down-type quark couplings to dark matter is an artefact of
unitarity violation. We provide three different solutions to this mono-W
problem in the context of spin-1 simplified models and briefly discuss the
impact that our findings have on the prospects of mono-W searches at future LHC
runs.
