A fresh investigation of a hitherto overlooked remark by the Atticist grammarian Irenaeus with a prescriptive content (akin to a note by Phrynichus), which is found in a branch of the ms. tradition dating back to the early Palaeologan age. It has been edited by Rutherford in his Phrynichus’ edition (1881) and since then has never been taken into account in the very few studies on this grammarian.