IBM Sues Groupon Over Business Model by Chris Morris @FortuneMagazine March 3, 2016, 9:25 AM EDT E-mail Tweet Facebook Linkedin Share icons Just as Groupon was starting to win back investors, it’s facing another potential crisis. IBM is suing the daily deals website, alleging it infringed on IBM patents. In a complaint filed at the U.S. District Court for the District of Delaware, IBM says it warned Groupon officials that the company’s business model was being built on patented technology, but those warnings went unheeded. Sign up for Data Sheet, Fortune’s technology newsletter. “Groupon has refused to engage in any meaningful discussions about reaching a license agreement to end its infringement of IBM’s patents,” IBM’s complaint said. This isn’t the first time Big Blue ibm has gone after an online deals site. Last year it accused the operators of the Priceline pcln websites of using four IBM patents to operate its travel and dining operations. For more on IBM, watch: For Groupon grpn , the suit comes just as the company’s stock is showing signs of a rebound. On Feb. 11, Groupon announced better than expected earnings and the company has seen its stock more than double since then to over $4.50 per share. That’s still far below its initial price though. When shares began trading in November 2011, Groupon’s stock was worth more than $26 per share. Reuters contributed to this story.