Berkshire-Hathaway said it bought more than 35 million shares of big bank JPMorgan Chase and 41 million shares of software giant Oracle in the third quarter. As of Sept. 30, the JPMorgan stake was worth $4 billion and the Oracle stake was worth $2.1 billion.

Berkshire also said it bought smaller stakes in another bank PNC Financial, as well as insurance company, Travelers.

The disclosures were made in Berkshire Hathaway’s 13-F form filed each quarter with the SEC.

Buffett has been gradually building up positions in major financial companies. Five of Berkshire’s ten largest holdings by market value were banks, including Bank of America, Wells Fargo, U.S. Bancorp and Goldman Sachs, according to CNBC. The firm also added to its stakes in Bank of America and Goldman in the third quarter.

Oracle joins Apple as Berkshire’s investments in the tech sector. In the second quarter, Buffett added to Berkshire’s Apple stake, currently it’s largest holding. Since then Apple’s stock has declined amid concern that iPhones sales in the current quarter would come in below what Wall Street had been expecting.

Berkshire has had some informal ties with JPMorgan. Todd Combs, one of Buffett’s investment managers, sits on the board of directors of JPMorgan. In July, Buffett and JPMorgan CEO Jamie Dimon wrote a joint op-ed urging companies to stop issuing quarterly earnings guidance. And in January, the two, along with Amazon CEO Jeff Bezos, formed a nonprofit venture to bring down health-care costs for their U.S. employees.

JPMorgan’s stock was up 1.7% in after-hours trading. Oracle’s stock was up nearly 3.7%, while PNC’s was up 2% and Travelers was up 1.6%.