A “looming budget vote” is keeping Vermont Senator Bernie Sanders from a scheduled appearance at Duke Chapel tomorrow.

Sanders, the former presidential candidate, was supposed to partake in a discussion with the Rev. William Barber as part of Duke’s 2018 Martin Luther King Jr. Commemoration and Duke Chapel’s Bridge Panel series. Barber is the former president of the North Carolina NAACP and is now national co-chair of the Poor People’s Campaign, a revival of King’s work.

All the free tickets for the event ,”The Enduring Challenge of a Moral Economy: 50 years After Dr. King Challenged Racism, Poverty and Militarism,” had already been snapped up.

According to the university, the event “is being postponed because of the likelihood of votes in the United States Senate that will require Sen. Sanders to remain in Washington. Effort are underway to reschedule the event.” All tickets will be honored at the rescheduled event.

Congress must pass a spending measure before Friday at midnight in order to avert a government shutdown. A shutdown appeared likely Thursday evening as Democrats and Republicans gridlocked over protections for DACA recipients, who were brought to the country illegally as children.