Pershing Square Capital’s Bill Ackman revealed a new strategy on Wednesday in his years-long bearish position on Herbalife.

The billionaire hedge fund activist has been betting against Herbalife for more than four years, accusing the nutritional supplement company of running a pyramid scheme.

Herbalife has always denied those allegations.

“We’ve been entirely right on our Herbalife investment in terms of the fundamentals of the business. We’ve been wrong on the share price. A big part of that is the fact that companies repurchase a huge amount of shares,” Ackman said on CNBC’s “Squawk Box.”

“A big part of this is trying to cause a short squeeze. We just did something, which we will announce later this afternoon,” he added. “What we did recently in the last few weeks is we converted our entire [Herbalife] short position into a put position. And as a result there is no longer an opportunity to squeeze Pershing Square.”

The investor said his firm has 3 percent of its capital in derivatives betting against Herbalife’s share price.

“Ultimately the [negative] fundamentals will prove right,” he said. “Because it is in the form of derivatives, the upside is great and we don’t have these risks associated with a short squeeze.”

Herbalife did not immediately respond to a request for comment.

The company’s shares are up 51 percent year to date through Tuesday versus the S&P 500’s 15 percent return.

Ackman has stumbled in recent years with high-profile losing bets on Valeant Pharmaceuticals and Chipotle Mexican Grill.

Pershing Square has been underperforming the stock market this year. The fund is down 1.2 percent year-to-date return through Oct. 24, according to its website.

Ackman also revealed in the interview that his fund’s return recently turned positive for the year.