Dictionary of English - none

But when none refers to a plural noun, doubts can arise. This is because the fallacious idea has been implanted in the minds of English speakers that none means 'not one' and therefore, like one, must have a singular verb. It conflicts with the natural tendency of the English language, which is to make the verb agree with the noun to which the pronoun refers – if the noun is plural, then the verb is plural.

The result is that in a plural context, both a plural verb: None of my friends were there and a singular verb: None of my friends was there can be used. In general, a plural verb sounds more natural and unaffected, and is to be preferred. It has the particular advantage that an accompanying plural pronoun avoids the sexist 'he' or 'she' and the ponderous 'he or she' in cases where the sex of the referent is unknown or unspecified: None of the directors of the company stand to lose their own money. And sometimes it would simply be ridiculous to insist on the singular – for instance, where none is used in specific comparison with a plural noun: None of our dancers are as talented as the Russians.