Amazon and Disney are in a dispute over Fire TV ad sales that could delay the addition of Disney’s upcoming streaming service to Amazon’s Fire TV devices, the Wall Street Journal reported Thursday.  Spokespeople for Disney and Amazon declined to comment.

At the core of the dispute is Amazon’s demand to sell a percentage of advertising on Disney’s ad-supported apps, according to the report. This doesn’t directly impact Disney Plus, which is scheduled to launch without advertising on November 12, but it could delay the launch of the service on Fire TV, and in an unlikely worst-case-scenario even lead to Disney apps disappearing from Fire TV devices altogether.

Amazon has been demanding to sell a percentage of the inventory of ad-supported apps on its Fire TV platform, with the Journal reporting that the company is now asking publishers to sell as much as 40% of the ads running within their apps. Disney has reportedly resisted this push.

Disputes about advertising in streaming apps aren’t new: Roku for instance has for years pushed publishers to let the company sell a share of their ad inventory. These demands have at times been met with resistance as well. Google doesn’t let Roku sell any of its ad inventory, which was one of the reasons that YouTube was absent from Roku devices for years.

Vevo resisted Roku’s demands in the past as well, and instead threatened to leave the platform, according to a source familiar with the situation at the time. The music video service remained on Roku without giving in to the device maker’s demands.

And while it’s unlikely that the current dispute between Amazon and Disney won’t be resolved, there is some precedent for these kinds of negotiations getting out of hand: Amazon clashed with Google over business terms for years, leading to Amazon not selling Google devices on its store, and Google blocking Fire TV users from accessing YouTube. The two companies finally resolved their dispute this year.

Amazon initially didn’t sell advertising within third-party apps, but  changed its tune as it recently began to build out its own advertising business.