Tudor Investment Corp.’s latest 13-F filing reveals that Paul Tudor Jones has recently doubled his bet against the stock market. In the second quarter, the fund bought put options on nearly $6 million of the SPDR S&P 500 ETF (SPY). The fund now owns put options on over 8.3 million shares of the SPY, which makes these put options the largest position that is held by the fund. The fund has also purchased call options on another 420,000 or so shares of the SPDR S&P 500 ETF, which brings the total number of shares on which it owns calls to about 1.43 million.

Put options allow the fund to profit if the price of the S&P 500 Index falls. The options give the fund the right, but not the obligation, to sell shares of the index at a set price, known as the strike price. If the index price moves below the strike price, then the fund can sell the shares at the higher strike price instead of the current market price.

Jones, the famous global macro hedge fund manager who is famous for his historic bet against the market before the “Black Monday” market crash in October 19, 1987, is not the only investor who is currently betting against the market. George Soros has also doubled his bet against the S&P 500 by buying put options on nearly 2 million shares of the SPDR S&P 500 ETF. He has made the statement that a British exit from the EU could cause an even greater calamity than “Black Wednesday”, when the value of the British pound dropped precipitously, or even the crisis with British refugees.

The markets dropped sharply when the Brexit decision was first announced, but they quickly rallied back to reach new highs. Many financial experts feel that the markets are in the late stage of a bull run. (For more, see: Top 5 Positions in Paul Tudor Jones' Portfolio.)