Apple’s iPhone 12 is the company’s first phone to support 5G, but if you were hoping to use dual SIM and 5G together, it won’t work — at least at launch.

That’s according to an internal company training document shared on Reddit and unearthed by MacRumors, which says it confirmed the document's authenticity.

“When using two lines in Dual SIM mode, 5G data isn't supported on either line and will fall back to 4G LTE. If customers are using eSIM only and are on a 5G supported carrier and service plan, they'll have 5G access,” the document says.

Apple’s newer iPhones, including the iPhone 12, have one physical SIM slot, but they also have a digital eSIM. This makes it possible to use the phone in dual SIM mode, meaning you can have two independent phone numbers, on two networks, in one phone. It’s a life-saver of a feature for users who have, for example, a private and business phone number, and want to keep them separate but don’t want to carry two phones. The lack of 5G while using dual SIM will likely be disappointing for these users.

However, according to MacRumors, which obtained a separate, internal Verizon slide, a fix is coming in the form of a software update “later this year.”

Apple’s iPhone 12 and iPhone 12 Pro will start arriving into customers’ hands on Oct. 23, so it might be a fairly long wait until the issue above is fixed. As for the iPhone 12 mini and the iPhone 12 Pro Max, they’ll be available a bit later, with pre-orders starting on Nov. 6. and availability starting on Nov. 13.