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A bstract We present cosmological constraints on the sum of neutrino masses as a function of the neutrino lifetime, in a framework in which neutrinos decay into dark radiation after becoming non-relativistic. We find that in this regime the cosmic microwave background (CMB), baryonic acoustic oscillations (BAO) and (uncalibrated) luminosity distance to supernovae from the Pantheon catalog constrain the sum of neutrino masses ∑ m ν to obey ∑ m ν < 0 . 42 eV at (95% C.L.). While the bound has improved significantly as compared to the limits on the same scenario from Planck 2015, it still represents a significant relaxation of the constraints as compared to the stable neutrino case. We show that most of the improvement can be traced to the more precise measurements of low- ℓ polarization data in Planck 2018, which leads to tighter constraints on τ reio (and thereby on A s ), breaking the degeneracy arising from the effect of (large) neutrino masses on the amplitude of the CMB power spectrum.