Transportation Security Administration officers who call out sick for a single day during the partial government shutdown can be disciplined if they don’t provide a doctor’s note documenting their illness.

Union representatives say the policy seems designed to pressure workers not to take absences while they continue to work without being paid. The Department of Homeland Security, which includes TSA, hasn’t been funded for 25 days due to a stalemate on Capitol Hill.

“I don’t know of any [workplace] that has you bringing a note after one callout,” said Joe Shuker, regional vice president at the American Federation of Government Employees and recently retired TSA agent at the Philadelphia airport. “They’re forcing these people to go to the doctor and pay $40 for a copay. They’re creating bigger problems for us.”

Callouts are a perennial problem at TSA whenever its 50,000 security officers are forced to work as “excepted personnel” and forgo pay due to a funding lapse. Absences are expected to increase if the shutdown continues beyond Friday, when workers will miss their entire paychecks for the first time since the shutdown began Feb. 14.

In a March 5 guidance memo viewed by HuffPost, TSA said that if a worker was sick for three days or less during the shutdown, management could require them to provide a signed and dated doctor’s note stating that the employee was “incapacitated” during the absence. An illness-related absence any longer than that could require more documentation.