The news this week that HBO Max — finally — was coming to Roku was welcomed by millions of the device maker’s customers, eager to stream the WarnerMedia service on their TVs and catch “Wonder Woman 1984” when it premieres on Christmas Day.

But there’s a wrinkle for some Roku users who want to get HBO Max.

Under its agreement with WarnerMedia, Roku is no longer selling the legacy standalone HBO channel through its Roku Channel store. That’s the same provision Amazon and Apple agreed to when they inked their HBO Max distribution deals — something WarnerMedia wanted in order to keep viewers in its own app experience and to collect first-party data. To encourage the transition to the plus-size HBO Max, it’s priced at the same $14.99/month as the old HBO standalone service.

Now, to access HBO Max, Roku customers who were already subscribed to HBO via the Roku Channel will first need to cancel their HBO subscription, as the device maker explains in a new document on its support site.

To unsubscribe from HBO on the Roku Channel using your computer or mobile device, customers can go to my.roku.com, select the “Manage your subscriptions” link and click “Unsubscribe” next to the “HBO on The Roku Channel” tile. On Roku devices, you can use your remote to highlight HBO on the Roku Channel and press the star button on Roku remote, then select “Manage Subscription” and choose “Cancel Subscription.”

After they’ve successfully done that, Roku customers must then search for the HBO Max app, install it from the Roku Channel Store, and follow the signup steps on the Roku device. Note that Roku now will sell subscriptions to HBO Max, using its Roku Pay payment service.

For Roku users who have already subscribed to HBO Max (either directly from WarnerMedia or another third-party distributor) or HBO Now, the process is much simpler. You can use your existing email and password to sign in to the HBO Max channel on your Roku device and verify access. If you’ve subscribed to HBO Now, the channel will automatically be updated to HBO Max (then select “Access all of HBO Max” when you open the app).

HBO Max is supported on all Roku devices that support OS 9.3 and later.

With the Roku deal, HBO Max now covers all the major OTT device bases, with Roku (46 million active accounts as of Q3) and Amazon Fire TV (more than 50 million monthly active users) representing the biggest chunk. HBO Max also is now available directly to Comcast Xfinity X1 and Flex customers, as well as Apple (iOS and Apple TV), Google (Android, Chromecast and YouTube TV), Xbox, PlayStation and Samsung TVs.

Meanwhile, earlier this month WarnerMedia introduced a limited-time HBO Max deal for direct subscribers that offers a 22% discount to new subscribers who prepay for six months at $69.99 (about $11.66 per month). The AT&T-owned company also ended HBO Max’s free seven-day trial ahead of the “Wonder Woman 1984” day-and-date premiere.