Boss uses a recruiter-approved coffee cup test in every interview—and he won’t hire anyone who fails it

• There’s another red flag test to have on your radar, this time involving coffee cups. One boss says he won’t hire anyone who fails it—and recruiters tell Fortune it actually works. 

Previously, we’ve heard from a CEO who rejects job candidates who say they can start right away and the sneaky salt and pepper test that plagues lunch interviews. 

Now, there’s a coffee cup test to add to job seekers' list of hoops they need to jump through to land a job in today’s tough market.

The trick was described by an Australian boss, Trent Innes, who is the former managing director of accounting platform Xeno, and now works as the chief growth officer at SiteMinder.

Speaking on the business podcast "The Ventures," Innes said he always takes prospective employees for a walk to the kitchen for a beverage—and although he calls it a coffee cup test, it’s not about whether you take your caffeine hit black or with sugar. You could even forgo coffee for water or tea and still pass the test. 

It’s what you do with your cup afterward that he’s keeping an eye on.

"Then we take that back, have our interview, and one of the things I'm always looking for at the end of the interview is, does the person doing the interview want to take that empty cup back to the kitchen?" Innes said. 

Unfortunately, those who have the right skills for the job but leave their dirty mug at the scene of the interview probably won’t hear back from the hiring manager. Innes thinks it’s a red flag that they're not the right culture fit for the company. 

"You can develop skills, you can gain knowledge and experience, but it really does come down to attitude, and the attitude that we talk a lot about is the concept of 'wash your coffee cup,'" the boss added.

Taking your used cup, mug or glass back to the kitchen highlights that you’re a team player, considerate, and care about the small things.

CEOs at Cisco, Amazon, and Kurt Geiger echo the importance of attitude  

It’s not what you know, or even who you know—countless CEOs have highlighted that success hinges on attitude. Like Innes, Andy Jassy has said that an “embarrassing amount of how well you do, particularly in your twenties” depends on it. 

“I think people would be surprised how infrequently people have great attitudes,” the Amazon CEO revealed. “I think it makes a big difference.”

Likewise, the CEOs of Pret and Kurt Geiger have both stressed that being nice to their boss and coworkers was one of the biggest determining factors in their success.

“You cannot teach positive attitudes and engagement and energy,” Cisco’s U.K. CEO Sarah Walker echoed recently in Fortune. 

That’s the No. 1 green-flag trait she keeps an eye out for when hiring or looking to promote from within—and she said it outweighs what’s on your resume, especially early in your career. 

“It’s more about the person first and foremost than it is about skills or experience,” she added.

Recruiters say the test actually works

If you want to test for attitude over aptitude, you’d be happy to learn that the coffee cup test actually works. 

Lewis Maleh, CEO of the global executive recruitment agency Bentley Lewis, says it’s one of many subtle tests he’s seen in his 20 years of recruiting experience—“and I think there's some real value to it.”

“I’ve found that these little behavioral observations can tell you so much about a person that you'd never catch in a formal Q&A,” he says, adding that employers could also watch how interviewees treat reception staff for similar intel.

“So much of hiring is about culture and fit and I think this is an important part of assessing whether someone would suit your organization.” 

But he wouldn’t pin entire hiring decisions on such tests. 

“I see it more as one piece,” he adds. “Go for it, but keep it in perspective. Not every great candidate will think to clear their cup, especially if they're nervous or unfamiliar with your office. Some might even come from work cultures where this wasn't expected.”

After offering to help an assistant clean up coffee cups people had left behind from a prior meeting, Saira Demmer says she landed a role at SF Recruitment. In the four years since, she’s been promoted to CEO. 

“It was between me and another candidate,” Demmer recalls. "I insisted on helping, and she fed back to the 2 MDs making the decision that she strongly felt I was the better fit for that reason.” 

“I don’t personally put people through this test, but I do think it’s a good one because it’s a real-life test of EQ, teamwork, and understanding of the environment around you,” she adds. 

“These skills are critical to success and a very good guide as to how likely someone is to have a positive impact on others or not. Culture is such a huge driver of business success that I would applaud any leader who takes the level of care to consistently look for these kinds of details.”  

This story was originally featured on Fortune.com