Lego A/S has hit a brick wall in the U.S.

After almost a decade of double-digit sales growth, the world’s second-largest toy maker said revenue rose just 6% world-wide in 2016, after a big marketing push in the U.S. failed to lift stalled sales there. Lego said U.S. sales were flat for the year.

Still, Lego’s revenue came within a hair’s breadth of surpassing that of longtime rival Mattel Inc., which has stumbled as a variety of its brands, including its American Girl and Monster High franchises, have lost appeal.

For the year ended Dec. 31, Lego reported revenue of 37.9 billion Danish kroner ($5.38 billion), up 6% from a year earlier. Net income edged up to 9.44 billion kroner from 9.2 billion kroner in 2015, while operating profit rose 1.7% to 12.4 billion kroner. Mattel, which also makes Barbie dolls and Hot Wheels toy vehicles, reported annual net sales of $5.46 billion in January.

Lego is struggling to maintain the strong growth it long enjoyed in some mature markets while simultaneously conquering new ones. Its latest results were a sharp slowdown from 2015, when Lego reported a 25% jump in revenue and a 31% rise in net income. They mark the slowest growth since 2007, when the company was in the middle of a turnaround.