In an interview with USA Today, Secret Service director Randolph Alles said that some of his agents have already hit the annual caps on their salary and overtime.

Under President Barack Obama, the total number of people with Secret Service protection was 31. Under Trump, that number is up to 42, 18 of whom are members of the president’s family.

Trump needs Secret Service protection every time he visits one of his other properties, as he has almost every week since his inauguration, and his four adult children need it every time they take a business trip or go on vacation.

According to Alles, he won’t be able to pay his agents for work they have already done, unless Congress comes up with extra cash. At the moment, the individual cap for combined salary and overtime is $160,000 per year. Alles wants that raised to $187,000, but even then there will be a shortfall in paying some agents for work they’ve carried out.

“The president has a large family, and our responsibility is required in law,” Alles said in the interview. “I can’t change that. I have no flexibility.”

While Trump’s family size may have exacerbated the problem, it didn’t create it. Last year, Congress also had to stump up extra funding to pay agents for thousands of extra hours that they had worked above the federally-mandated overtime cap.