The Daily Camera reports that about 1,200 students are scheduled to take the exam for an introductory chemistry class at the same time as Colorado’s caucuses, which begin at 7 p.m. Tuesday.

Chemistry department chairman Carl Koval says canceling and rescheduling the exam would be a logistical nightmare.

So he decided that students who talk to their professors in advance can get an excused absence. Because those absences normally require documentation, like a doctor’s note, Koval asked students to take a selfie to prove they were actually at the caucus.