Millions of T-Mobile customers with family plans of at least two lines will soon be able to watch Netflix for free, as the wireless company announced today that it will include a free Netflix subscription for these multi-line plans.

Starting on Sept. 12, 2017, folks with T-Mobile ONE family plans with at least two lines will be able to have T-Mo cover the cost of the most popular Netflix account ($9.99/month). The offer will be available to both new and existing T-Mobile subscribers.

When the offer goes live next week, T-Mobile customers will have to activate the option via the T-Mobile app on their phone. This will provide them with a link to connect your T-Mo and Netflix accounts.

Be aware that both companies caution that it could take 1-2 billing cycles for T-Mobile to start paying that Netflix bill for you, so until then you’re responsible for making sure your subscription is current.

The $9.99/month plan only allows streaming on two devices simultaneously, so what if you want (or already have) the $11.99/month Netflix plan that gives you up to four streams at the same time? Both T-Mo and Netflix tell Consumerist that people with this pricier plan would only be responsible for the $2/month above what T-Mobile pays Netflix for the standard plan.

It’s also worth pointing out that while the $9.99/month Netflix plan includes streaming in HD, T-Mobile ONE limits the video resolution of cellular streaming. T-Mobile customers who want true HD over cellular would need to pay for the more expensive T-Mobile ONE Plus plan.

Today’s T-Mobile announcement could set off a content-subsidy battle among wireless companies. AT&T has been trying to leverage its ownership of DirecTV, offering discounts for customers with AT&T phone and DirecTV satellite TV service, or not counting online access to DirecTV Now against the data limits of AT&T customers. AT&T is also in the process of acquiring Time Warner, and has been using free or discounted rates for that company’s HBO premium network in an apparent effort to boost its DirecTV Now numbers.