Any improvement in their relationship could clear the way for the largest bank by market cap to do more business with billionaire Musk or his constellation of companies, which also include SpaceX and social media platform X. Meanwhile, Musk could tap into JPMorgan’s deep supply of capital and services.

But the clash of the business titans reportedly got very testy around 2016. That’s when JPMorgan turned down Musk’s request for the bank to underwrite leases for Tesla’s EVs, citing uncertainty over how to value the batteries, the WSJ said.

Musk called the bank, screamed at the head of consumer banking at the time, and threatened to pull Tesla’s commercial banking business, sources told the WSJ, with one saying Musk ended his rant with “F*** you.” That angered Dimon, who told Musk that JPMorgan wouldn’t be bullied, the report said. 

A spokesman for JPMorgan declined to comment to Fortune. Tesla didn’t immediately respond to a request for comment.

Relations got worse, with JPMorgan suing Tesla in 2021, claiming it was owed money for a trade the bank helped arrange in 2014. Tesla countersued, and the lawsuits are still ongoing.

But the WSJ pointed to signs of a thaw: In November, Dimon called Musk a “brilliant human being” who is making “unbelievable contributions to mankind.” In January, Musk complimented Dimon in a tweet after the bank boss said Donald Trump was right about the economy, immigration, and China.

And in March, Musk showed up at a JPMorgan technology event at a Montana resort and spoke with Dimon on stage for an hour, then stopped by Dimon’s suite where they spoke for another hour. Afterward, sources told the WSJ that Dimon decided JPMorgan could try doing business again with Musk.

Meanwhile, Musk is looking for more allies on Wall Street and on capital markets.

He is trying to win shareholder support for his historic $47 billion compensation package from Tesla, which has gotten intense criticism.

Elsewhere, Musk’s AI company, xAI, is seeking investors; it raised $6 billion in a venture capital round last month that puts the not-even-a-year-old startup at $18 billion.