Warren Buffett’s Berkshire Hathaway notched more than $8 billion in gains on Friday as Apple stock rose more than 5% on a strong earnings report.

Apple reported December quarter earnings on Thursday, posting nearly $124 billion in sales and strong sales growth in every product line except for the iPad. Investors seemed particularly keen on CEO Tim Cook’s remarks that supply chain headaches are improving.

Berkshire Hathaway started accumulating Apple stock in 2016 and now owns 887,136,000 shares of the iPhone maker, or over 5% of Apple’s outstanding stock, according to FactSet data.

Buffett has been one of Apple’s biggest supporters since 2016, although he initially considered high-flying tech investments to be too risky for Berkshire Hathaway before he started buying Apple shares. Apple now makes up over 40% of Berkshire Hathaway’s portfolio.

Apple issues regular dividends, which Buffett has said is attractive under his investing philosophy.

“I don’t think of Apple as a stock. I think of it as our third business,” Buffett told CNBC in 2020, calling it “probably the best business I know in the world.”

Buffett has also made the argument that Apple’s iPhone ecosystem is “sticky” and encourages customers to regularly upgrade, making it a safer investment and more like a consumer company than a tech company.

Cook has also praised Berkshire’s investment in Apple. “We run the company for the long term. And so the fact that we’ve got the ultimate long-term investor in the stock is incredible,” Cook told CNBC in 2019.

The mutual admiration between the two business titans goes beyond investment, though. In 2019, Apple briefly published a game based on Buffett’s childhood that was presented at the Berkshire Hathaway shareholder meeting.