The tech sector has seen many relatively new startups taking their company’s public quickly, with at best mixed results. Now the CEO of the Nasdaq stock exchange has some advice for tech startups: take your time going public. Bob Greifeld of Nasdaq shared the advice to tech startups in an interview on CNBC’s Squawkbox earlier this week. In the talk he called going public too soon “the worst thing in the world” for young tech companies.

There are a variety of reasons for startups to put off their initial public offerings. Current securities rules are relatively favorable to small companies and their investors. Further, private capital is flourishing and so interested in investing in the tech sector that they are routinely creating new “unicorn” companies funded to the tune of $1 billion or more.

Greifield says that over the past decade, the typical time for startups to go public has doubled. He advised companies to be fully mature before their initial public offering, noting that such a step triggers increasingly rigorous reporting requirements that companies must be ready for.

He noted that the Nasdaq hopes to cash in on this trend, through its Nasdaq Private Markets division, which recently acquired SecondMarket, a company that works to enable private security investments.

Despite some companies putting off their IPOs, Griefield said that the IPO market is still strong, despite a severe drop this last quarter. Proceeds from IPOs in the third quarter were just $7.3 billion, down more than 80 percent from the near-record setting quarter at this same time last year. That quarter featured the IPO of Alibaba, the massive Chinese internet commerce site, which was the largest-ever global stock market debut.

The Nasdaq currently has a backlog of 77 IPOs, which Greifield says is typical for the exchange.