In other countries, prize-linked savings accounts are a popular vehicle used to encourage low-income people to build nest eggs. The premise is simple: saving money enters customers into a lottery, with relatively modest prizes. Since the accounts became legal in the U.S. in 2014, some banks have launched their own versions, and now Walmart and its prepaid debit cards are joining the party.

Is Walmart’s goal to give its MoneyCard customers an incentive to load up as much money as possible on their card? Not exactly. Instead, the apparent intention is to give MoneyCard users a reason to put more of their money aside as savings.

Prizes enter the picture when customers put money in the Vault, with every dollar deposited serving as an entry in the sweepstakes. There are 500 prizes every month, with a top prize of $1,000.

“According to The Federal Reserve Board of Governors, nearly half of all U.S. families can’t cover a $400 emergency with their savings,” Walmart’s senior VP of services for U.S. stores said in a statement. “That’s a reality we don’t want our customers to have to live with, and we thought we could help.”

Walmart quietly introduced the program back in August, and brags that customers using it are saving 35% more than they did before the program began.

The sweepstakes may work to get people to stash away more money, and for the very few winners it is likely a nice surprise. However, it’s worth noting that this sweepstakes is replacing the one traditional reward of a savings account: interest.

“There are no additional fees to use the Vault,” Walmart’s helpful FAQ explains, “but money in your Vault does not earn interest.”

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