U.S. consumer credit in December grew by the most in nearly a year due to a sharp increase in credit card usage, a potentially positive sign for the economy.

Total consumer credit rose by $18.8 billion to $3.1 trillion, the Federal Reserve said on Friday. That was the biggest gain since February 2013.

Economists polled by Reuters had expected consumer credit to rise by $12 billion in December.

Revolving credit, which mostly measures credit-card use, rose by $5 billion in December after climbing $465 million in November. Revolving credit figures can be volatile.

Non-revolving credit, which includes auto loans as well as student loans made by the government, increased $13.8 billion in December.