Mobile carrier T-Mobile added YouTube, the single biggest source of mobile video traffic, to its list of online video services that customers can stream without penalty Thursday, a move that may appease FCC scrutiny of the program.

T-Mobile’s “Binge On” program, which lets customers stream video and music from some companies but not all, is a popular perk among consumers trained to keep a close eye on how much data they’re eating up on their phones. But it and other programs like it have raised eyebrows at the Federal Communications Commission, which has asked whether this freebie viewing unfairly stacks the deck against some companies.

Also Read: Love Free-Data Streaming? US Government Isn't So Sure

Binge On launched in November at a splashy unveiling event, allowing unlimited use of major streaming services like Netflix, Amazon and HBO Go, but it lacked the biggest one of them all: YouTube.

YouTube is the single biggest source of mobile network traffic in North America, accounting for nearly 21 percent of all the data that mobile devices gobble up during peak hours, according to researcher Sandvine.

But the FCC has wondered if T-Mobile’s selective data buffet skirts a gray area of what’s known as “net neutrality,” the principle that traffic on the Internet should be treated equally and that carriers shouldn’t be able to prioritize some companies’ content over others. A month after YouTube criticized T-Mobile for degrading the quality of its streams even though it wasn’t participating in the program, Chairman Tom Wheeler said he was asking T-Mobile and others with similar options for more information about them at a press conference in January.

Also Read: T-Mobile Gives Customers Unlimited Data to Stream Netflix, HBO, Hulu

In what appeared to be another move to appease regulator worries, T-Mobile also announced on Thursday that it would give video providers more choice over the resolution of their video. One option lets providers manage their video stream themselves when a Binge On customer begins streaming something from them, instead of T-Mobile’s systems.

YouTube will be one of the first services participating in that plan.

Alongside the YouTube addition, T-Mobile said it added Discovery GO, ESNE TV, FilmOn.TV, Fox Business, Google Play Movies, KlowdTV and Red Bull TV to Binge On.