  In the Standard Model (SM), the Higgs mass around 125 GeV implies that the
electroweak vacuum is metastable since the quartic Higgs coupling turns
negative at high energies. I point out that a tiny mixing of the Higgs with a
heavy singlet can make the electroweak vacuum completely stable. This is due to
a tree level correction to the Higgs mass-coupling relation, which survives in
the zero-mixing/heavy-singlet limit. Such a situation is experimentally
indistinguishable from the SM, unless the Higgs self-coupling can be measured.
As a result, Higgs inflation and its variants can still be viable.
