Fake it ‘til you make it can be terrible business advice.

Take it from former U.S. presidents George W. Bush and Bill Clinton, political opposites who both agree that it’s better to admit when you don’t know what you’re doing.

“I think it’s really important to know what you don’t know, and listen to people who do know what you don’t know,” Bush recently said at a leadership event in the Bush Center in Dallas. Clinton also agreed that those in power – especially those “who are real arrogant in office” – will be judged poorly by history.

Former U.S. presidents Bill Clinton (L) and George W. Bush agree it’s good to ask questions. (Stewart F. House/Getty Images)

The problem is, even if admitting you don’t know something is the smartest play, many employees are afraid it will make them look stupid. No one wants to be that guy who stammers “I don’t know” when called on in a meeting, or to admit he’s in over his head when assigned a big project.

When Kyle Boze, then 25, was first promoted from a marketing specialist to a global marketing manager at a medical device company, he confessed to his boss that he didn’t know where to start with a new service feature the company hadn’t used in years. “I was ridiculed by him for it, and made to look like I did not know what I was doing, for simply admitting that I needed help,” Boze told Moneyish.

But then again, Boze also gained sales experience at another company by openly admitting he was new to it, but with a more supportive manager. “I was continually asking questions to gain clarification upon my own background,” he said, “and I eventually started our own Inside Sales organization. So it all depends on the culture of an organization.”

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The need to know all of the answers gets drilled to us in school, research shows, and we never really outgrow it. But saying “yes” to an assignment you’re uncomfortable with and asking questions later – or trying to B.S. your way through an answer – can easily backfire.

“It might keep your job for another week or another month, it might make people think you are good, but that’s not the point,” said Stephen Levitt, the co-author of “Freakonomics” in a 2014 podcast. “Really, the goal is to be good and to improve and to learn and to make things better. And the only way to do that is to start by saying, ‘I don’t know.'”

That’s something Peter Shankman, 44, learned the hard way. The entrepreneur and CEO of The Geek Factory, Inc., a social media, marketing and PR strategy firm in New York, told Moneyish that he nearly blew an assignment at his first job, working the AOL newsroom overnight in the 90s.

“I had to put together a photo essay, and it involved cropping photos and collating images and getting up online, and I said, ‘I got this, no problem!’” he recalled. “Everyone left for the night, and I’m sitting there like, ‘I don’t know what I’m doing. I’m screwed.’ The first time I tried putting it together, I ended up saving a file with nothing on it.”

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He fortunately found someone else working the late shift who helped him put the package together on deadline. “I survived, but it taught me that you have to be smart about how you fake it,” he said. “Over the years, I have said ‘yes’ to things I didn’t know how to do, and then I learned how to do them. But don’t put yourself in a corner. Always make sure you have a way out.”

Or just ‘fess up upfront. Those three little words – “I don’t know” – can actually save you a world of trouble later – if you use them the right way, and with the right people.

“The reality is, it’s really easy to tell when somebody doesn’t know something. They hedge around the answer,” leadership coach Kristi Hedges told Moneyish. “The stronger way to address that is is to simply say, ‘I don’t know the answer to that, but I’m going to find it.’ That takes a lot of confidence.”

But never just stop at saying, “I don’t know.” Your admission will go over better if it’s made part of an action-oriented statement, like, “Let me tell you what I do know, and what I’m still learning,” or, “Let me get back to you on that by the end of the day,” which shows you’re working on finding the answer.

“I was surprised how people reacted in the boardroom to, ‘I don’t know it off the top of my head, and need to research it further,’” said Steve Driz, president and chief architect at The Driz Group. “The response has been surprisingly neutral. While most expect you to know your trade, everyone understands that everything changes too fast, and there is no way that one can know it all.”

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But the sooner you ‘fess up, the better, because nothing ticks off a manager more than wasting their time by handing in something that’s completely wrong, let alone unfinished.

Shankman also recalls the time he hired someone to build a website, and the developer got back to him a week after it was due, apologizing that the project was too involved for him. “I”ll never hire that guy again,” Shankman said. “If you don’t know something, and you tell me that upfront, it’s fine, but now I have to hire a new developer and start from scratch, and that kills me.”

If you’ve waited too long to admit you don’t know what you’re doing, however, then it’s better to say “yes” to your employer first, and figure the rest out later.

“People can damage their credibility by asking things they should already know, like something that is supposed to be a core part of your job,” Hedges said. If you’ve been working at a company for six months, you should have picked up on how to file an expense report, or learned the name and face of your CEO. But if you don’t know, “in those situations, it’s best to nod your head ‘yes’ and then find the info from a trusted colleague later,” said Hedges.

But generally, having the guts to admit you’re not a know-it-all not makes you appear to be more trustworthy and credible, according to a Harvard study. “And there is an element of flattery in asking someone for more information, or seeking out their advice, because it shows you think highly of them and you are investing your time in them,” Hedges said.

Admitting “IDK” works for bosses, as well. “It actually shows openness and curiosity, which are good adjectives around leadership,” said Hedges. “To be willing to say, ‘I don’t know,’ can be really powerful to those who work below you, because it shows there’s room for you to grow, and it sets an example for everybody.”