It’s long been known that Silicon Valley has a monochromatic white-bro culture in which minorities and women are severely underrepresented. But a problem that is just as serious is only now coming into focus: The tech industry is ageist as well. If you’re of a certain age and you’re looking for a job in tech, you need not apply.

The evidence is in plain view. In 2007, then-22-year-old Facebook founder Mark Zuckerberg told an audience at Stanford that when it comes to hiring people, “I want to stress the importance of being young and technical. … Young people are just smarter.”

Zuckerberg has since taken back that remark, but Facebook’s hiring record still reflects his advice. The average age of the company’s employees is 29, according to Payscale. And Facebook isn’t an anomaly: At LinkedIn, the average age is 29, at Google and Amazon it’s 30, and at Apple it’s 31.

Zuckerberg isn’t the only Silicon Valley honcho to air ageist views about older workers. Prominent venture capitalist and former Sun Microsystems founder and CEO Vinod Khosla echoed them when he said, “People under 35 are the people who make change happen. People over 45 basically die in terms of new ideas.”

In an in-depth investigation by the New Republic titled “The Brutal Ageism of Tech,” Noam Scheiber reports on what he found interviewing dozens of people about the issue during the course of eight months. His conclusion: “Silicon Valley has become one of the most ageist places in America. Tech luminaries who otherwise pride themselves on their dedication to meritocracy don’t think twice about deriding the not-actually-old.”

There’s evidence that not only is ageism rampant in Silicon Valley, but it may be more widespread than racial and gender bias. Bloomberg reports that between 2008 and 2015, 226 complaints of age discrimination were filed with the California Department of Fair Employment and Housing against the 150 largest tech companies in Silicon Valley — 28% more than racial bias complaints and 9% more than gender bias complaints.

In the most visible recent instance of ageism, 54-year-old JK Scheinberg, the Apple engineer who spearheaded the company’s move to Intel processors for the Mac, applied for a job at an Apple Store Genius Bar. Scheinberg, who had retired, figured he’d be a shoo-in for the job. After all, who could be more qualified to give help about Apple products? After a group interview in which he was twice as old as everyone else in the room, he was told by all three interviewers, “We’ll be in touch.” When they didn’t get back to him, he called to follow up. Again, no interest. Eventually he got an email setting up a second interview. But by then he had no interest in working for a company that didn’t want him because of his age.

Perhaps the best insider’s view of ageism in the tech world comes from Dan Lyons, tech journalist and writer for HBO’s Silicon Valley. Lyons worked for 20 months at the tech company HubSpot, starting when he was 52 and the average age of his HubSpot co-workers was 26. He found that ageism was in the company’s DNA and wrote a book about his unhappy experience there, Disrupted: My Misadventures in the Start-Up Bubble. Here’s what he had to say about it in a recent article: “The lesson I learned is that when it comes to race and gender bias, the people running Silicon Valley at least pay lip service to wanting to do better — but with age discrimination they don’t even bother to lie.”

All this needs to be fixed. But before that can happen, tech companies need to admit there’s a problem, which they’re reluctant to do. For example, Slack this year updated the data it publishes to show the company’s diversity and included for the first time the percentage of LGBTQ employees in its workforce. (It was 13% as of December 2015). That kind of transparency about LGBTQ is good. But why is there no information about the age of its employees?

It’s time for the tech industry to face up to its ageism, and then fix the problem. Until it does, it can’t call itself truly inclusive, no matter how much it pays public attention to its race and gender biases.