Elon Musk accused the Microsoft billionaire in a tweet last week of betting as much as half-a-billion dollars that shares of the electric-car company would fall. 

In a text exchange between the two billionaires leaked online that Musk said was authentic, the Tesla CEO asked Gates if he was still shorting the stock. Gates said he was, and that he wanted to talk to Musk about philanthropy. Musk denied the request outright.

“Sorry, 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 reportedly said in the text exchange.

But Gates told the BBC in an interview Wednesday that his bet against Tesla is unrelated to advocacy for pro-environmental projects and government policies.

“That has nothing to do with climate change. I have ways of diversifying,” Gates said in an interview. 

He added that just because he was betting against Tesla doesn’t mean he was against the rise of electric cars.

“The popularity of electric cars will lead to more competition for selling those cars. So there’s a difference between electric cars being adopted, and companies becoming infinitely valuable,” he told the BBC.

Musk and Gates have a history of frosty relations, and Musk has attacked Gates on Twitter repeatedly. 

After Gates said he was concerned about the range and premium price of Tesla vehicles in a 2020 video with YouTuber Marques Brownlee, Musk said in a tweet that his conversations with the former Microsoft CEO “have been underwhelming tbh.” 

More recently, amid Musk’s takeover of Twitter, the Tesla and SpaceX CEO tweeted a picture of Gates side by side with an emoji of a pregnant man, saying, “in case u need to lose a boner fast.”

Gates told CNBC’s Squawk Box in July 2020 that Musk should cut back on his controversial vaccine comments and focus on electric cars and rockets. In a New York Times podcast later that year, the Tesla CEO responded to Gates’ comments about Musk’s lack of experience with vaccines, calling Gates a “knucklehead.” Musk has also attacked Gates in tweets regarding his vaccine advocacy.

In a tweet last week, Musk said he was moving on from attacking Gates for shorting Tesla. But Gates appears unruffled.   

“There’s no need for him to be nice to me,” Gates said of Musk in the BBC interview. 

Disagreements and attacks between the two men have drawn outsize attention because of their immense wealth. Musk overtook Gates as the world’s second-richest person in 2020 and later surpassed Amazon founder Jeff Bezos to take the top spot. The Tesla CEO is currently the richest person in the world, according to the Bloomberg Billionaires Index, while Gates sits at fourth on the list. Gates has pledged to give away most of his fortune over his lifetime.