T-Mobile is reportedly considering building a multibillion-dollar fiber network that it would use to provide home internet service, according to Bloomberg. While the company started testing fiber internet last year, its main home-focused offering connects with 5G instead of other wired infrastructure like DSL or cable.

Bloomberg reports that the carrier has been working with Citigroup to find financial partners for a potential $4 billion joint venture or “commercial partnership.” It seems like early days for the plan, and it’s possible nothing will come of it, but it still feels like a significant step for the wireless carrier, which has traditionally used and managed a very different kind of infrastructure.

Meanwhile, T-Mobile’s current home and business internet offerings (at least the ones that are widely available) rely on its 5G and LTE networks. While that does allow it to roll out coverage more easily than if it had to lay fiber in the ground, there are limitations; poor service can lead to a bad user experience, and a fiber network will almost certainly outperform a cellular one. For T-Mobile, it’d be good to be able to offer both options in some areas: a relatively inexpensive cellular option for people with relatively light internet needs and a fiber offering for power users and people who require rock-solid service.

T-Mobile didn’t immediately respond to The Verge’s request for comment on its search for partners to build a fiber network and about how many users are currently on its fiber home internet pilot. When we wrote about that service in August last year, T-Mobile had only made it available in parts of New York City and was using a local fiber provider’s infrastructure instead of its own. According to Bloomberg, the carrier has also been looking into other partnerships where it could make a similar arrangement.

While T-Mobile may be looking to spend big on fiber, it seems likely that its main home internet offering will still be its fixed-wireless service. As Google has shown, building out a fiber network in just a few dozen areas can be an expensive and time-consuming operation, one fraught with potential pushback from established players. Earlier this year, T-Mobile announced that a million people had signed up for its 5G home internet service and that it was capable of providing it to over 40 million households.