New Jersey’s governor has said that a “serious software error” at the state’s department of motor vehicles led to around 6,600 non-US citizens being registered to vote, and that “fewer than 400” of them wrongly cast ballots.

Governor Mikie Sherrill said in a statement on Tuesday that the error occurred between June 2023 and June 2024. It affected people who indicated that they were not US citizens while applying for driver licenses.

Nineteen US states allow non-US citizens to obtain drivers licenses. Non-citizens are not allowed to vote in national elections.

The error comes as US President Donald Trump pushes for a national law to require proof of citizenship and ID to vote.