It is correct in the latter case, incorrect in the former. It largely doesn't matter, but recruiters I know, for example, throw out resumes for this particular error (though one had heard some schools actually encourage the practice, to the student's disservice) and some people (myself included until I thought better of it) think less of authors who make it. Linguistics as a discipline is descriptive, but people who are not linguists treat people differently for making errors.
but recruiters I know, for example, throw out resumes for this particular error
That's nuts.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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