ARISTOTLE, METAPHYSICS Z 1029a6

[...]if the true substance is what is prior, then individual form is the true substance. [...]the reading favours the idea that the true substance is the composite, whilst according to Alexander the individual form, as in the case of human intellect, is substance in a more proper sense. [...]it is possible to suppose that if he had had the opportunity, he would have chosen the reading in his lost commentary and in his other works, as in the extant passage from his De anima, which is presumably a quotation from Metaphysics 3. [...]both readings can be defended on the basis of those conflicting interpretations.3 However, I think that such a doubt about the right reading is philosophically worthwhile, because it rules out the possibility of taking Metaphysics 1029a6 with the reading of modern editions as evidence in favour of the interpretation of substance as individual form.