The District of Columbia’s Board of Elections says a challenge has been raised to having Vermont Sen. Bernie Sanders on the ballot for the city’s Democratic presidential primary.

Board spokeswoman Margarita Mikhaylova confirmed a challenge has been filed. The board’s website says the challenge was filed March 24 by an individual, Robert Brannum. Mikhaylova said she couldn’t elaborate further on the challenge.

Brannum, a schoolteacher, is a former president of the D.C. Federation of Civic Associations. He didn’t immediately respond to a voicemail left by The Associated Press requesting comment.

Mikhaylova says a hearing on the challenge will be held April 6 but she wouldn’t say what agency would be involved.

A Sanders campaign spokesman said in an email that he’s confident Sanders will be on the ballot June 14.