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Q: I work in a small office, and there are some things that just never seem to get done—think cleaning up the office kitchen and restocking bathroom supplies—unless I’m the one that does them. Sometimes my boss asks me to do these things, and sometimes I’ll just go ahead and take care of them because I figure it’s better to be proactive, right? But then I wonder if it’s a bad idea or I could be hurting my career if my colleagues just think of me as the one to come to if we’re out of paper towels. Should I stop doing them on my own? And is there a way I can politely and professionally tell my boss I don’t want to do these things—at least not all the time?

A: You might be the only office Cinderella at your job, but your situation is vexingly common. Women spend an average of five hours a week doing "office housework," like cleaning the communal kitchen, planning staff parties, and other non-job-related tasks, said Laurie Weingart, senior associate dean of education at Carnegie Mellon University's Tepper School of Business.

In a new study, Weingart found that when it comes to what she termed “non-promotable tasks,” women are two to three times more likely than men to volunteer to do these jobs or be asked to take them on.

Your hesitation isn’t unfounded. This dynamic contributes to what researchers call “vertical gender segregation,” which is an academic way of saying that accepting all of these extra duties in the name of being a good team player is really a bad career move. The time women spend doing literal and figurative “office housework” cuts into the time they need to do their actual jobs, and that can reflect poorly on them when performance reviews roll around.

Read next: 7 Things You Can Use Your #Woman Card to Cash In On

What good is being a team player if it’s holding you back? People might remember the surprise baby shower you orchestrated for your supervisor, but that’s not the kind of thing you can put on your resume—and it’s definitely not the kind of thing that’s going to get you promoted.

There are two common types, Weingart said. First is "the people who automatically say yes without thinking twice, and they harm their career without knowing it because they are spending too much time working on things that aren’t part of their job." They may feel good about helping, she said, "but they don’t realize that they are bearing a burden that others aren’t.” The other category is women (like you!) who want to say no but are afraid that doing so could hurt their working relationships or reputation among colleagues.

But you can break this cycle if you think strategically—and stick to your guns when the requests roll in. The trick is choosing when to push back.

For example, not all menial tasks are necessarily non-promotable. “Promotable tasks can also come from doing work-related favors for others who are likely to reciprocate,” she pointed out. If the favor-seeker is someone higher up the corporate ladder, doing the odd job could help build your network. The caveat here is that you don’t want every one of your interactions with this person to consist of you performing some menial task on their behalf.

There are ways to decline without labeling your coworkers a bunch of sexist jerks. First, evaluate what’s being asked of you. “If somebody asks me to do a favor that won’t help my career, I should ask myself, ‘Is it my turn, or is there a male colleague who could do it with me?’” Weingart said.

“You should pitch in, but you should be choosy about when you do,” she advised. If it always seems to be “your turn,”make sure that you’re not the only one shouldering the burden, and make sure that both your female and male coworkers are participating.

If there’s a legitimate business reason why another colleague might be better suited to the task at hand, recommend that person and articulate why. If it really is a non-promotable task (washing the dishes in the office sink, cleaning the bathroom, or the like) suggest someone else—and try to make it a guy.

“Maybe you recommend a peer who is a male,” Weingart suggested. “If you’re concerned about raising the sexism piece of it, you can send the same message indirectly by saying, ‘I’m not available to help out this time, but maybe Joe can.’” If the job is a regularly recurring one, propose a rotating schedule so everyone pitches in equally.

And don’t throw a fellow female colleague under the bus, Weingart added. “You don’t want to be the one to fall prey to recommending another woman just because you know that person is likely to say yes.”