In the first quarter, Berkshire Hathaway (BRKA), Buffett’s investing and insurance conglomerate, added nearly 2.6 million shares of the computer giant. Based on IBM’s average price of around $160 per share during the quarter, Buffett beefed up his investment in IBM (IBM) in the first quarter by roughly $400 million. At the end of the first quarter, Berkshire held 79.5 million shares of the company, for a stake worth nearly $13 billion.

IBM’s shares were down by 14% last year, and some have questioned Buffett’s bet on the company. IBM has aggressively used cash to buy back its stock, a move Buffett has often criticized companies about. At Berkshire’s recent annual meeting, during the near day-long question and answer session, Buffett was pressed on his IBM investment. Buffett’s long-time investment partner Charlie Munger responded that IBM is a wonder company and that many of Berkshire’s best investments have had reversals in the past.

At this year’s Berkshire annual meeting, where Buffett’s many companies display their wares, often for sale, attendees could challenge IBM’s Watson to a game of Jeopardy, or taste food that was prepared using recipes created by the super computer.