The post, in reply to an anonymous user commenting on the Gates Foundation’s offloading of Microsoft stock, breathes new life into Musk’s conflict with Gates, which dates back to 2022.

Gates reportedly shorted, or bet against, Tesla’s stock to the tune of $500 million, earning him a personal text from Musk and “super mean” behavior, Gates said in a later interview with Musk biographer Walter Isaacson. The Tesla CEO at the time asked Gates bluntly if he had taken the short position, which the Microsoft cofounder confirmed, though he added in the message he wanted to talk about philanthropy possibilities.

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Why is Elon Musk still feuding with Bill Gates?

How much has Gates lost on Tesla short?

What triggered Musk’s recent comments about Gates?

Musk, though, balked at the idea.

“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,” he said in a message at the time.

He followed up with a post on X making fun of Gates’ weight. Gates for his part said the short “has nothing to do with climate change. I have ways of diversifying,” he told the BBC.

Despite Musk’s animosity, which Gates later explained away—“he’s super mean to so many people, so you can’t take it too personally”—Musk’s Tesla has turned the tables on Gates.

It’s unclear exactly when Gates opened the short position, but since April 2022, when the exchange between Gates and Musk was publicized, the EV company’s stock has shot up at least 20%, but possibly more depending on the price Gates shorted the stock at.

Gates’ bet had him underwater by $1.5 billion when the stock was trading at $400 per share, according to Walter Isaacson’s biography of Musk. The stock as of Monday was trading at about $408 per share.

The reestablished feud between Gates and Musk comes as Musk, who has a net worth of $431 billion, according to the Bloomberg Billionaires Index, likely cemented his place as the world’s richest man for years to come thanks to a massive pay package approved by Tesla shareholders earlier this month.

The largest CEO compensation plan ever proposed would give the Tesla CEO up to $1 trillion in compensation in exchange for his meeting of certain performance benchmarks, including boosting the stock to an $8.5 trillion market value, more than any other company in modern history.

This story was originally featured on Fortune.com