Investment bankers are concerned there may be big corrections on the way for “tech unicorns,” private companies valued at over $1 billion, according to a new survey by BDO USA.

The horns on those unicorns could cause another tech bubble to burst. A 52 percent majority of the 100 capital markets surveyed by BDO expressed concerns about the valuations of the so-called unicorns. BDO pointed out that last year some of the unicorns went public to get access to more funding, but their valuations turned out to be a lot lower than their most recent round of private financing.

For example, Twilio, a provider of communication software for other tech companies, recently completed a highly successful IPO, with its stock nearly doubling on its first day of trading last month, after pricing above its most recent private valuation. While that was good news for other tech businesses considering an IPO, Twilio had a private valuation of a little over $1 billion and, according to BDO, was too small to be considered a bellwether for larger unicorns such as Uber, Snapchat and Airbnb.

“In recent years, the widespread availability of private funding at attractive valuations has led to a dramatic drop in the number of IPOs coming from the technology sector, the historical leader in offering activity,” said Lee Duran, a partner in BDO’s Capital Markets Practice, in a statement. “Instead, there are now more than 140 technology businesses privately valued at more than $1 billion, yet just one of these companies has pursued an IPO in 2016 as they fear their private valuations won’t stand up to scrutiny in the more discerning public markets. As new rounds of private financing reflect more realistic valuations, unicorns will increasingly be faced with a choice between being acquired or going public. Either way, the actual profitability of these businesses will be given much greater weight versus projections of future performance.”

According to the survey, if private valuations continue to surpass those of the public markets, a 55 percent majority of the capital markets executives polled by BDO expect some of the tech unicorns to fail. When asked to predict how many could falter, the consensus was that about 17 percent of the unicorns would not survive. Maybe they should be added to the endangered species list.