(Bloomberg)—Amazon.com Inc. surpassed Wal-Mart Stores Inc. as the world’s biggest retailer by market value after a surprise second-quarter profit sent the e-commerce company’s stock into record territory.

Amazon shares rose as much as 20% to $580.57 on Friday, giving the Seattle-based company a value of about $272 billion. That compares with Wal-Mart’s $233.2 billion market capitalization.

Amazon’s share price fell back sharply by the end of the day, closing at $529.42. That still left Amazon with a stock market value of $246.5 billion, compared to $230.5 billion for Wal-Mart.

Wal-Mart, No. 3 in the Internet Retailer 2015 Top 500 Guide, still dwarfs Amazon (No. 1) in terms of sales, with about five times its annual revenue. But Amazon has solidified its dominance in e-commerce, forcing its big-box rival to play catch-up. Wal-Mart is investing heavily in its web operations and developing its own online subscription service to compete with Amazon Prime.

Amazon’s market value has been steadily gaining on Wal-Mart’s this year. Amazon was already up 55% in 2015 through Thursday’s close, while Wal-Mart has slid 16%.

Amazon posted revenue of $23.2 billion last quarter, a 20% gain. That topped analysts’ average projection of $22.4 billion. Net income was $92 million, or 19 cents a share, the company said. Analysts had estimated a loss of 14 cents.