After billionaire Bill Gates downplayed Elon Musk’s ill-fated attempt to short Tesla shares on Twitter, the Tesla CEO responded.

Elon Musk has criticized Bill Gates for not being serious about fighting climate change, claiming that he made a “half-billion dollar” wager against Tesla.” At the moment, I’m working on my own stuff,” she says of her future plans.

Musk retorted, “Sigh,” when Gates claimed he had spent more money on climate change than Musk or anyone else.

“I give a lot more to climate change than Elon or anyone else,” Gates said. “I give a lot of philanthropic dollars, I back companies – you know electric cars are about 16% of emissions, so we also need to solve that other 84%.”

It’s over a month since Musk revealed he turned down an offer to work with Bill Gates on charity. Musk released a text message exchange in which he confronted Bill Gates about his purchase of $500 million in shorting Tesla stock.

Before Musk could ask if Gates still had a “half billion dollar short position against Tesla,” the technology investor said that he and his wife were planning to meet him.

“Sorry to say I haven’t closed it yet,” Gates said. “I would like to discuss philanthropy possibilities.”

Musk then blew him off, saying he couldn’t take Gates’ offer seriously “when you have a massive short position against Tesla, the company doing the most to solve climate change.”

Shortly before Elon Musk posted a highly offensive tweet comparing Bill Gates to the pregnant man symbol, Kostya Yushchenko said in an interview with The Verge that Elon Musk was “a real scumbag.”

We’ve yet to hear from Gates on this tweet.