The payments giant had prohibited using its technology for online gaming in the U.S. in 2003, following its merger with eBay (EBAY). Over the past few days, however, PayPal has started appearing on a few U.S. gambling sites including Caesars Interactive’s WSOP.com website.

A spokesperson for PayPal (PYPL) told Fortune that integrating with gambling sites is a limited test with four operators including Caesars Entertainment (CZR). Gamblers can use PayPal to fund their online accounts with the sites.

PayPal’s rules continue to prohibit transactions using its technology for gambling except for approved merchants in locations where gambling is legal. PayPal is available for many European gambling sites, for example.

Until its ban, PayPal was popular among U.S. online gambling sites. But after regulators questioned their legality, PayPal stopped making its service available to the gaming industry.

Now that PayPal is an independent company, it is looking for new ways to bring in more revenue from its core payments business. According to research from Morgan Stanley, the U.S. online gambling industry’s revenue could hit $5.2 billion in 2020, if more states legalize it.

Currently, the only U.S. states where online gambling is legal are Nevada, New Jersey, and Delaware.

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