While Olympic athletes go for the gold, they’re also earning some by promoting popular brands. But recent changes to the Olympic marketing rules may harm their ability to do so.

Everyone’s eyes are on Simone Biles right now. The world champion gymnast is making headline after headline, and companies are capitalizing on her success. Biles has deals with Nike, Core Power, and GK Elite Sportswear—and that’s just right now. Michael Phelps, the most decorated Olympian of all time, can boast deals with Subway, Under Armour, Visa, Speedo, AT&T Wireless, and Power Bar. Another popular trend in Olympic marketing, however, is “ambush” marketing.

When companies give free gear to athletes because they know it will be worn on camera, like Dr. Dre’s Beats headphones, they’re using athletes to market their product. Some companies reach out to athletes individually and ask them to wear their products while running or working out on camera. But changes in the marketing rules at the Olympics may undermine these efforts.

For the 2016 Olympics in Rio, the International Olympics Committee (IOC) amended one of their rules to state that athletes can not endorse non-official sponsors of the Olympics during the Games and can’t use specific terms like “effort” or “performance” in their ads.

These attempts to cut down on athlete marketing are aimed to give the actual sponsors of the event their fair turn in the sun. For instance, Panasonic paid $350 million for an eight year Olympic games sponsorship. With this rule, known as Rule 40, the Olympics are trying to prevent other companies from poaching their turf.

The wording states:

No athlete participating in the Games may allow his or her person, name, picture or sports performance to be used for advertising purposes during the blackout period for each Games (which generally corresponds with the period of time that the Olympic or Paralympic Village is open) unless a waiver is sought from and granted by the USOC.

While you may not be able to pay Gabby Douglas to wear a t-shirt with your startup’s name on it, there are plenty of other ways to incorporate the Games into your marketing strategy.