SACRAMENTO (CBS / AP) — More than 3 million Californians with federally compliant Real ID driver’s licenses will have to provide a second proof of address after the Department of Motor Vehicles failed to ask for it.

The Sacramento Bee reports the Department of Homeland Security sent a letter to Gov. Gavin Newsom Monday informing him that the DMV did not follow federal guidelines when processing the documents.

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The DMV says 3.4 million Californians have obtained Real ID licenses. The department plans to contact them.

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The agency says people can make up the requirement by returning a letter from the DMV by mail. They can visit a field office or check online.

Americans must have Real ID cards by October 2020 if they want to board airplanes or enter federal facilities without using a passport.

Last month, the acting director of the DMV warned Californians who are seeking the Real ID cards to expect longer lines at offices through the summer.

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