  Stability of the Higgs vacuum during early universe inflation is dependent on
how the Higgs couples to the spacetime curvature. Limits on the curvature
coupling parameter at the electroweak scale $\xi_{EW}$ are shown to be
consistent only when quantum gravity effects are included and a covariant
quantisation procedure, such as Vilkovisky-DeWitt, is adopted. Stability
requires $\xi_{EW}>-0.03$ for a top quark mass $M_t=173.34\,{\rm GeV}$.
