We show that a previously neglected process -- the decay of $\bar{\Lambda}_b$ baryons to antihelium -- can greatly enhance the cosmic ray antihelium flux. Such $\bar{\Lambda}_b$ baryons frequently occur as intermediate states in dark matter annihilation into heavy quarks or gauge bosons. Due to their antibaryon number and 5.6 GeV rest mass, they effectively decay to multi-antinucleon final states with small relative momentum which can bind into antihelium. We find that $\bar{\Lambda}_b$ decays increase the antihelium signal by up to two orders of magnitude and possibly even account for the tentative observation of $\mathcal{O}(10)$ antihelium events at AMS-02.