The partial government shutdown is expected to hit one group of workers particularly hard ... and it’s not members of Congress.

While roughly 800,000 government employees have already begun missing paychecks because of the shutdown and likely won’t see back pay until after it’s resolved, another subset of workers isn’t going to be paid at all.

Hundreds of contractors in federal buildings including janitors, security guards, and cafeteria servers are not only experiencing a sharp break in their work schedules, they also won’t be compensated for this pause, according to 32BJ SEIU, a labor union that represents many building service workers caught up in this shutdown. Additionally, thousands of contractors in roles ranging from IT to project management to research are potentially caught in a similar bind.

Government employees typically receive back pay after the shutdown is over, but contractors are paid directly by companies that can’t bill the government for services when it’s shut down. Because these companies won’t get paid, they, in turn, aren’t able to pay their workers.

Some workers have returned to their jobs and will continue to receive their salaries uninterrupted, depending on the funding source their contracts rely on, according to 32BJ spokesperson Frank Soults. Contractors at the Statue of Liberty are being funded by the New York state government during the partial shutdown, for example.

Others, meanwhile, have been told that they could be seeing a gaping hole in their paychecks.

“My supervisor told me we won’t be getting paid,” Bonita Williams, a janitor at the State Department told the Washington Post, “so my bills won’t be getting paid.”

Soults said that members of the union will continue to have health care coverage for at least 30 days from the start of the shutdown.

It isn’t the first time that low-wage contractors have been forced to bear the brunt of a shutdown’s effects: A similar issue emerged in 2013 when the government was closed for 16 days and many contractors faced severe cutbacks in their hours.

“It is a cowardly disgrace,” Héctor Figueroa, the president of 32BJ SEIU, said in a statement.

Congress members, meanwhile, will see no breaks in their pay whatsoever. Unlike other government employees, they won’t even have to rely on back pay because their salaries are written into the Constitution and will be continuous throughout the shutdown.

A growing number of lawmakers, including Sen. Chris Van Hollen (D-MD), and Reps. French Hill (R-AR) and Elise Stefanik (R-NY), have said they’d like their salaries withheld until the partial shutdown is over. Others including Sens. Mazie Hirono (D-HI) and Richard Blumenthal (D-CT) are donating their salaries during this time.

The government officially went into a partial shutdown in late December after lawmakers were unable to reach an agreement over funding for Trump’s border wall. Now that the new year is in full swing, the shutdown’s effects are becoming increasingly apparent.

The president has said that workers support the shutdown. Unions disagree.

While federal employees and contractors are the ones most likely to feel the impact of a shutdown, Trump has claimed that they support his effort to close down the government over the border wall, and shown little empathy for the position this political fight puts them in.

“Many of those workers have said to me and communicated, ‘stay out until you get the funding for the wall,’” he said in December. “These federal workers want the wall.”

Not so, says groups including 32BJ SEIU, the International Federation of Professional and Technical Engineers, and the American Federation for Government Employees, all of which are unions representing government employees or contractors.

“The president falsely claims that ‘many’ federal workers support the shutdown and have told him to ‘stay out,’” says IFPTE President Paul Shearon in a statement. “We have not heard from a single member who supports the president’s inaction. Most view this as an act of ineptitude.”

Representatives of the National Border Patrol Council, a union representing border patrol agents, have said they back Trump’s efforts to get a border wall even if it means that workers won’t be paid, however. (Meanwhile, Customs and Border Protection officers are among the people suing the federal government for requiring workers to be on the job without pay.)

Contrary to Trump’s claims, many unions aren’t egging the shutdown on so much as aggressively urging the president and Congress to work toward a solution that would reopen the government.

As things stand, it’s not exactly clear what that solution will look like.