Arizona’s voter registration system pulls information from the state’s driver’s license database as a method of proving citizenship, but the Maricopa County Recorder’s office found a flaw with the database, which incorrectly showed that some people provided proof of citizenship when they applied for a driver’s license.

The issue affects just a tiny fraction of the roughly 4.1 million people registered to vote in Arizona — roughly 98,000 voters who got a license before Oct. 1, 1996, said Arizona Secretary of State Adrian Fontes on Tuesday.

“That’s the day when Arizona started requiring proof of legal presence in the United States to get a driver’s license,” Fontes said.