Progressive members of Congress have rallied around the Raise the Wage Act, which would raise the minimum wage to $15 by 2024. But they may want to fix a glaring income inequality issue in their own offices first.

Of the nearly 190 members of Congress co-sponsoring the $15 minimum-wage legislation, the vast majority don’t pay their own interns a penny. The analysis, conducted by the right-of-center Employment Policies Institute, found that only 10 of the co-sponsors of the bill offer their interns any compensation whatsoever, usually in the form of a stipend.

Minimum-wage jobs and internships are, of course, different things. People support families on the former, while the latter aren’t permanent and are mostly aimed at students trying to gain professional experience and bank some extra money (sometimes to pay for their college education).

But there’s a principle of fairness around both.  Carlos Vera, founder and executive director of the non-profit bipartisan group Pay Our Interns, said it was hypocritical for the Democrats pushing for a $15 minimum wage to expect their own interns to work for free.

“I think it’s important to practice what you preach and ensure that your values are aligning with your actions,” said Vera.

For instance, Rep. Keith Ellison has tweeted that “Americans deserve nothing less” than $15 an hour. He also said that the increased hourly wage “isn’t too much to ask from corporations booking huge profits.” (No comment from his office on whether it’s too much to ask Congress to pay interns.)

Last month, Rep. Nancy Pelosi said that if Democrats took back the House in 2018, “in the first 100 hours we will pass a $15 minimum wage.” And Sen. Chuck Schumer added that he will “continue fighting tooth and nail” to impose the minimum-wage increase on businesses.

We reached out to each of these members of Congress to see how they reconciled unpaid internships with their calls for $15-an-hour pay. They did not respond.

Unpaid internships, which many companies also offer, are fairly commonplace on Capitol Hill. About half of Republicans and one-fourth of Democrats offer them, according to Pay Our Interns. Even so, critics say, unpaid internships can provide an unfair advantage to middle- to upper-income college students; their low-income counterparts may not be able to work for free for a summer, however good the experience would look on their resume.

Sen. Bernie Sanders is the only Raise the Wage co-sponsor who pays his interns an hourly rate. It’s $12—less than $15, but on par with the minimum hourly pay the Raise the Wage Act would establish in 2020. (The legislation raises the minimum wage slightly each year until 2024, when it reaches $15.)

Sen. Elizabeth Warren’s website says interns “may be eligible to receive stipends from our office,” but only if they’re not receiving outside funding or academic credit for the internship.

Jillian Kay Melchior writes for Heat Street and is a fellow for the Steamboat Institute and the Independent Women’s Forum.