Moments after making a plea for people to get out and vote in the Missouri primary Tuesday, Kansas City Mayor Quinton Lucas was turned away from the polls and told by a poll worker that he “wasn’t in the system” to cast his ballot.

Lucas showed up to vote at 7am in the same place he said he has voted since 2009. Soon after, he posted a message on Twitter saying he was not allowed to cast a ballot because a poll worker could not find his registration.

Election officials later blamed the incident on a mistake by a poll worker, and Lucas returned later in the day and voted. But the mayor said the incident pointed to a larger problem in how elections are run.

When Lucas tried to vote, his name didn’t come up as a registered voter when a poll worker searched his name using a utility bill he brought, or even by using his Kansas City Board of Police Commissioners’ ID. He was offered a provisional ballot, but declined, saying he wanted to make sure his vote was registered so that if anyone checked his record it would show he voted.

“If the mayor can get turned away, that would mean anybody can … so it’s something we all need to try to address,” Lucas said, adding that he was finally able to cast his ballot by using his passport as ID.

Missouri elections are managed by the Secretary of State.