A popular gauge of fear and volatility on Wall Street surged on Thursday and was nearing its highest level since U.S. Election Day amid rising geopolitical tensions centered on North Korea.

The CBOE Volatility Index VIX, -2.38% , or VIX, jumped about 44% to 16.04. That’s still below its historical average of around 20, but underlines an escalating sense of trepidation around global events. At the least, it may be reflecting growing expectations a stock market that’s knocked out repeat all-time highs without much of a break may be primed for a substantial downturn.

Thursday’s rise in the VIX represents its highest level since Nov. 8 when it hit 18.74, and its sharpest single-session climb, also since May 17, when it jumped 46%, according to FactSet data.

Indeed, U.S. stocks, which tend to move inversely with the VIX, were trading firmly lower. The Dow Jones Industrial Average DJIA, -0.87% ended off about 200 points, or 0.9%, at 21,847, while the S&P 500 index SPX, -1.11% finished down sharply, off 35 points, or 1.5%, at 2,438. Showing the sharpest losses was the Nasdaq Composite Index COMP, -1.07% down 2.1% at 6,216.

The downdraft for the equity market comes amid rising geopolitical tensions, after a North Korean army commander said “sound dialogue” isn’t possible with U.S. President Donald Trump and “only absolute force can work on him,” according to state media. North Korea also laid out detailed plans of how it would launch a missile strike on U.S. military bases in Guam.

The recent testy exchange underlines mounting tensions between Pyongyang and Washington, which accelerated on Aug. 8 when Trump said from his golf resort in Bedminster, N.J., that aggressions from North Korean leader Kim Jong Un would be met with “fire and fury like the world has never seen.” Wall Street investors are fretting that the intensifying rhetoric could risk an all-out nuclear war between the nations.

Against that backdrop, the VIX has been steadily rising over the past three sessions coinciding with a pullback in stocks and a jump in demand for assets perceived as havens, including gold US:GCZ7 which settled at a two month high and 10-year benchmark Treasurys TMUBMUSD10Y, 0.701% , which were hovering at yearly yield lows around 2.20%. Bond prices move inversely to yields.

The VIX measures options bets on the S&P 500 30 days in the future and has been muted mostly because there have been more market participants willing to sell “insurance” against a market drop than those willing to buy protection against such a fall. As a result, values of the VIX have been on the decline—until recently.

Because stock prices sink faster than they rise, the VIX is often viewed as a proxy for risk in the broader equity market. There’s a risky dynamic afoot that has reflected a protracted level of calm, sparking cautionary comments from DoubleLine Capital founder Jeff Gundlach and others of late.

However, the VIX has headfaked on the upside before only to carve out to fresh lows. It hit a low of 9.36 on July 21, a relatively short two months after the aforementioned recent peak in May.