German sporting goods group Adidas has reported a net loss of four million euros ($4.8m; £2.74m), blaming the costs of its takeover of Reebok.
Adidas is currently in the middle of a patent row with rival Nike
The fourth-quarter loss compares with a net profit of 20m euros a year earlier, and was worse than forecasts.
Sales for the period were up 27.2% to 1.52bn euros, boosted by strong demand for football products ahead of the World Cup.
Adidas bought Reebok for $3.8bn in a bid to take on market leader Nike.
However, a third-quarter sales slump for Reebok has sparked fears of a costly revamp at the US firm.
"Many of our current efforts will now focus on turning around the Reebok brand," said chief executive Herbert Hainer.
Despite the problems at Reebok, net profits for the full year were up 21.8% to 383m euros, with sales up 13.2%.
Adidas is currently in the middle of a spat with Nike, which filed a patent infringement suit against the company last month claiming that a number of its rival's trainers copied its technology.
US giant Nike said the Adidas shoes in question infringed its "Shox cushioning" patents and demanded damages from its German competitor.
Adidas shares were down 3.2% at 159.65 on Thursday.