AT&T announced on Wednesday that it has turned on call validation displays for certain Android phones. That way, you can easily determine if you’re getting a spoofed robocall or a call from a spammer.

If you’re using a Samsung Galaxy S10, Galaxy S10+, or an LG V40 ThinQ and you get a call from a number that AT&T has authenticated, you’ll now see a green check mark to the right of that number and a message saying that it’s a “Valid number.”

Here’s what that message looks like:

If you subscribe to AT&T’s Digital Home Phone service, you can also turn on call validation, and AT&T says you’ll see a “[V]” next to a valid number. AT&T also validates calls if you’re an iPhone user, but right now, there’s no way to know if a call is authenticated when you see the number on your screen — instead, you have to check your call log after the fact.

AT&T is authenticating numbers using the SHAKEN/STIR standards, and it’s rolling call validation out as part of its robocall-blocking AT&T Call Protect service, which it now offers for free to customers. For more about how SHAKEN/STIR works, you can read an overview here, but it’s effectively a universal digital authentication system for weeding out spoofed calls.

It’s important to note that not all carriers have implemented SHAKEN/STIR yet, so AT&T’s call validation may not be as effective as it could be. Of the four major carriers, only AT&T and T-Mobile have rolled out authentication for calls made between the two networks. Verizon says on its website that it is “working hard” to implement SHAKEN/STIR, and Sprint said in a November 2018 letter to the FCC that it would begin testing SHAKEN verification in the second half of 2019.

But as more carriers implement SHAKEN/STIR, AT&T and others should be able to better validate more numbers so that you can know when a call is spam.