Analysts have been carefully watching over the past week to see if Bitcoin would form a "death cross." And on June 21, the cryptocurrency passed that threshold.

A “death cross" certainly doesn’t sound good, but what is it exactly? Crosses are technical patterns in price charts: They point to a rapid shift in price compared to long-term performance of a stock, cryptocurrency, or the overall market. When the 50-day average physically intersects the 200-day moving average on a chart, it forms a cross, and it can serve as indicator of future price movement.

Golden crosses can point to impending bull movements. A death cross is a little more unsettling, as it has been known to precede some of the worst bear markets in history.

“It's not a welcome sight for bulls when you see the formation,” Nathan Cox, Chief Investment Officer at digital asset-focused investment firm Two Prime, said in an email. And yet, the death cross is exactly what emerged on Bitcoin’s price charts yesterday, and it’s “top of mind for all technical analysts,” Cox said.

On June 21, Bitcoin’s 50-day average fell below its 200-day moving average, triggering a death cross signal and causing reason for concern to some investors. On Tuesday, its price briefly fell below $29,026, temporarily erasing its 2021 gains, before climbing back above $32,000.

There could be a host of contributors to the decline. For one, China has recently been cracking down on crypto mining, and it banned financial institutions from offering crypto services earlier this year. Bitcoin tends to be hyper-sensitive to headlines, particularly those involving Elon Musk or Tesla.

Causes for the downturn aside, the emergence of the death cross on Bitcoin’s price charts has some investors on edge or perhaps moving to sell their stakes. Others have decided it's a good time to buy, or simply to stick with the pre-existing strategy.

Death cross dread

Death crosses reflect significant decline in stock or market prices, and have in some cases pointed to further downturns. Death crosses have previously signaled bearish behavior across the broader markets (think: 1929, 1938, 1974, and 2008).

For Bitcoin, this isn’t its first run-in with the death cross signal.

Bitcoin experienced a severe drawdown in March 2020—but by the time the death cross signal emerged on the coin’s price charts, Bitcoin had already moved past its lows, Cox points out. The price rallied shortly thereafter.

Bitcoin’s most substantial death cross was in the wake of the 2017-2018 crash, Cox notes. That’s when Bitcoin dropped around 60% between December and February. The death cross occurred on March 30, 2018, but lows had already been reached. Bitcoin rallied over the next month.

By definition, the death cross is an indicator of what has already happened—it isn’t always an accurate signal for bearish movements still ahead. Periods of decline can also be followed by intense gains, or even a golden cross.

The death cross may be regarded as a reliable indicator for impending low prices, but it’s not a perfect one, Cox said.

Many crypto investors are used to market swings, and some see a downturn like this as a good opportunity to increase their long-term positions.

At Voyager Digital, a crypto trading app, Bitcoin is in the top 10 of net buys of digital assets in the past 24 hours, and the top over the last seven days, according to Voyager CEO Steve Ehrlich.

“Historically, crypto has emerged even stronger on the other side of dip cycles,” Ehrlich said in an email.

As for how long a downturn could last, Cox says a rebound may depend on some of the external factors at play, such as whether Bitcoin miners in China are able to relocate quickly.

“If the narrative doesn't change,” he said, “we could see continued pressure on digital assets,”

This story was originally featured on Fortune.com