My, how Small Business Saturday has grown.

American Express introduced its Small Business Saturday promotion in 2010 to encourage people to shop locally and support small businesses (and, of course, to use AmEx cards). Held the Saturday after Thanksgiving, it’s meant to be an antidote to the blowout sales at big-box megastores on Black Friday. Last year, AmEx said, consumers spent $16.2 billion at local small businesses on the designated day.

This year, American Express’ support of small business is expanding beyond one Saturday — and it’s offering an extra incentive for AmEx cardholders to get involved. From now through Dec. 31, 2016, American Express cardholders can earn double rewards on spending at a participating small business, both in the store and online. So if your AmEx card normally gives you 1 point per dollar spent, you’d get 2 points per dollar at participating businesses.

To find local businesses where you can earn the 2X rewards, check out American Express’ Shop Small map. Plug in a ZIP code to see participating stores, restaurants and other merchants. You can also enter the name of a small business to see if it’s eligible for the bonus rewards.

Cardholders must register their cards for the promotion to earn the 2X rewards. There is one big caveat: If your card already gives you bonus rewards in a category — such as 6% cash back at supermarkets when you use Blue Cash Preferred® Card from American Express — you won’t earn 2X rewards on those purchases. The promo applies only to purchases eligible for a card’s base rewards rate. Check here for more information on how bonus rewards will be applied.

American Express isn’t the only issuer that’s offering bonus rewards on specific spending during the holidays. Check out the Nerds’ guide to the best credit cards for Black Friday and the holidays to see how you can earn extra rewards at Amazon.com, department stores, wholesale clubs and more.

Ellen Cannon is a staff writer at NerdWallet, a personal finance website. Email: ecannon@nerdwallet.com. Twitter: @ellencannon.

The article AmEx Doubles Rewards at Small Businesses Till End of 2016 originally appeared on NerdWallet.