A new promotion says you can sign up at $55 (or more) and be confident the price won’t increase… but be sure to read all the fine print.

It’s always a nasty surprise when any service tells you that the price you’re paying every month is going up for no reason. Comcast has been a fairly constant source of that particular anxiety, especially for its Xfinity broadband service in the US. But now it’s promising that it won’t raise rates for 5 years… if you jump through a few hoops.

Digital Trends reports that there’s a lot of fine details in the fine print of the announcement. First, you have to be a new customer—if you’ve been using Xfinity for years, you’re apparently unworthy of this consideration. New users don’t have to sign a contract, and they’re able to get the price lock without a commitment. But home internet plans that qualify for the 5-year lock start at $55 per month, versus $40 per month if you do sign a contract for just one year. For the cheaper plan, there’s no guarantee about the price beyond that. Oh, and the offer is only good until June 23rd, according to the promotional site.

Update: A Comcast representative reached out to me and said that the company intends to make the offer available to current customers “later this month,” and that though the current terms say the opportunity expires in June, they “intend to extend this beyond that date.” Nice.

So yeah, that’s a bit of a dice roll if you’re trying to save money on these less-expensive options. (For international readers: Yes, $40-55 per month is pretty cheap in the US, especially in metro areas.) If you’re fairly certain that you’ll be sticking with Comcast for the long haul—or you have no other choice, since much of the country operates with effective monopolies on wired internet service—then signing up at the $55 rate might make sense. You’ll have the option to drop it in a heartbeat if you see a better deal, say, on 5G-based service from Verizon or T-Mobile.

But if you don’t think you’ll be in the same area for that long, or if you’re pretty sure you’ll be switching away between 1 and 5 years from now, then the cheaper contract option probably makes more sense.

With my deepest apologies, I might suggest you break out the calculator if you’re on the fence. And if you’re planning on holding an internet service provider to any commitment that it makes about prices staying low… well, maybe set your expectations low, too.