Elon Musk is putting his money where his mouth is.

On Monday, the CEO of Tesla Inc. (TSLA) bought 33,000 shares worth about $9.85 million in the electric car maker, according to a SEC filing. Musk, Tesla’s biggest shareholder, now holds an almost 20% stake in the company, according to data compiled by Bloomberg.

Musk’s biggest stock purchase since March 2017 was revealed shortly after he criticized people shorting Tesla. On Friday, the tech mogul warned on Twitter that bears will regret their decision to bet against the electric car maker. “The sheer magnitude of short carnage will be unreal,” he wrote. “If you’re short, I suggest tiptoeing quietly to the exit.” (See also: Musk Promises 'Short Burn of the Century')

Source: Tesla Inc.

According to financial analytics firm S3 Partners, short interest in Tesla exceeded 40 million shares for the first time last week after Musk controversially dismissed questions being posed to him on a conference call as "boring.”  

The CEO's outburst came after Wall Street continued to warn investors that the electric car maker is bleeding cash. Analysts are skeptical about the company’s ability to execute on its high-volume Model 3 production plan and argue that a consistent failure to meet output goals will soon lead Tesla to run out of cash and tap investors for more. Tesla has raised about $9.23 billion since 2017.

Musk recently said Tesla will meet its production target of 5,000 Model 3s per week by the end of June and turn a profit in the second half of the year, despite planning to shut down the company’s Fremont, California factory for 10 days in the second quarter

Tesla’s share price rose nearly 2.95% on Monday, but is down about 2.8% over the course of 2018. (See also: Tesla Stock Bouncing Back After Musk Misfire.)