Carson Block is certain that markets need short sellers “more than ever.” The problem: a relentless stock rally and fresh regulatory challenges are weighing on his bearish peers struggling to raise capital.

For more than a decade investors have “stopped being remunerated for caring about risks,” fueling a speculative fever across markets, the Muddy Waters founder said Friday in an interview with Bloomberg Television. On top of the US stock market’s bull run and threats from regulators, Block lamented the US Securities and Exchange Commission is making it harder for whistleblowers to get paid.

“It’s easy to demonize short sellers as part of a populist message and somehow call us the suits,” he said. “The market needs short sellers more than ever given the amount of games that are being played, but if the long-side doesn’t care, this can continue — until it doesn’t.”

Block doubled down on his bearish call toward commercial real estate CLOs and even sees “interesting” opportunities for shorts among regional banks but pointed to all the threats short sellers face.

The Muddy Waters executive also affirmed his bearish bet on Blackstone Mortgage Trust, citing troubles with multifamily properties. He expects a dividend cut in the second half of the year. In December, Block revealed that he took a short position in the Blackstone trust, which makes loans collateralized by commercial real estate, saying that it faced a potential liquidity crisis.

The trust did not immediately respond to a Bloomberg request for comments. Shares of Blackstone Mortgage Trust rose after Block’s comments and are up 1.5% to $19.24 at 11:28 a.m. in New York. The stock is still set for a nearly 10% decline this year.

Carson Block has been gathering money for a fund that will bet on rising metals and mining stocks. The Muddy Waters Resources Fund filed a private placement notice in June with the SEC, indicating the vehicle initially brought in about $1.5 million. Earlier, this year his firm launched their first long-only fund focused on Vietnam, the rationale behind which includes a view that China is “uninvestable,” founder Block told Bloomberg Television in March. He sees Vietnam as a potential beneficiary of redirected capital flows.

This article was provided by Bloomberg News.