U.S. Sen. Kamala Harris, D-California, has withdrawn from being the commencement speaker at UC Berkeley’s spring 2018 graduation, according to an email from University Development and Alumni Relations sent May 7.

According to the email, Harris chose to withdraw because of the UC-wide speaker boycott called by the American Federation of State, County and Municipal Employees Local 3299, the UC system’s largest employee union. AFSCME 3299 will be on strike May 7–9 in protest of alleged unequal worker treatment and a contract forced by the university.

Chancellor Carol Christ will deliver the commencement address, according to the email. Christ also delivered the commencement address for the winter 2017 graduation.