It is uncontroversial that Proto-Indo-European *-nti# regularly becomes -t /d/ in Old Irish, as in berait ‧berat ‘(they) carry’ (< *b^heronti).  Nevertheless, my principal claim in this talk is that just in the copula, and under certain specifiable conditions, the same sequence results instead in -n.  In the course of using this new phonological rule to uncover a couple of hitherto unnoticed copular forms, I also comment on morpho-phonological curiosities in the paradigm of the Old Irish copula more generally.