Most scholars nowadays reconstruct a static root present with an alternation between lengthened grade in the active singular and full grade in the active plural and in the middle. I am unhappy about this traditional methodology of loosely postulating long vowels for the proto-language. What we need is a powerful theory which explains why clear instances of original lengthened grade are so very few and restrains our reconstructions accordingly. Such a theory has been available for over a hundred years now: it was put forward by Wackernagel in his Old Indic grammar (1896: 66-68). The crucial element of his theory which is relevant in the present context is that he assumed lengthening in monosyllabic word forms, such as the 2nd and 3rd sg. active forms of the sigmatic aorist injunctive.