Elon Musk called out former Microsoft CEO Bill Gates again for shorting Tesla’s stock, casting doubts on his goodwill in fighting climate change given the latter’s multi-billion-dollar bet against the electric carmaker.

In a series of Twitter posts, Musk disclosed Gates’ short position would now require up to $2 billion to close out. The position was initially $500 million before the business “went up a lot,” according to the Tesla CEO.

The share price of Tesla has seen a 20-fold increase since 2019, from $37 a share back in 2019 to the current trading value at around $760 per each, reaching an all-time high late last year of $1,222 per share, a 30-fold increase.

“Since Gates still has a multi-billion dollar short position against Tesla while claiming to help with global warming, I guess I have some trust issues with him too,” Musk wrote on May 27.

It is not the first time for him to question Gates’s commitment to help to address climate challenges, as the later has been betting on the Musk-operated electric vehicle company’s stock prices dropping. Musk previously had confirmed a leaked text exchange with Gates, unveiling that the former world’s richest person admitted to short-selling Tesla shares. According to the conversation record, Musk turned down the other’s request “to discuss philanthropy possibilities.”

“Sorry, but I cannot take your philanthropy on climate change seriously when you have a massive short position against Tesla, the company doing the most to solve climate change,” Musk said.

Gates’s media relations team didn’t respond to a request for comment by press time.

“I don’t think whether one’s short or long Tesla is a statement about your seriousness about climate change,” Gates told The Wall Street Journal in early May. “I applaud Tesla’s role in helping with climate change,” he added, but did not not directly address his Tesla short position.

The billionaire also approves of Musk’s potential impact on Twitter, suggesting that the latter’s plan to purchase the platform would allow for more so-called misinformation to proliferate. “That’s not his track record,” Gates told the Wall Street Journal.

The Tesla CEO has said he would restore free speech to the platform that he described as having “a very far-left bias” and vowed to stop what he calls “woke mind virus.”

Musk’s recent remarks followed a now-closed Twitter poll, asking his followers whether they trust billionaires or politicians less. The result was nearly 76 percent of the 3.4 million respondents voting that they trust politicians less.

Some users then started targeting other billionaires in reply. One asked if he thought Amazon founder Jeff Bezos was “(generally) a good person?”

“He’s fine,” Musk wrote in response, but called for more effort from his rival on the ongoing space race, and “less partying.”

Bezos previously questioned whether Twitter will fall under the influence of Beijing, hours after Musk secured a $44 billion buyout of the social media firm.