If you exceed your data plan’s limit on T-Mobile, you aren’t cut off entirely from the Internet. Instead, T-Mobile throttles your speed, downgrading it to somewhere between 64Kbps 128Kbps.

But if you use a speed testing app after hitting the limit—like Ookla’s Speedtest.net—it will measure the current network speed, not how slow your throttled connection actually is.

The FCC forced some concessions from T-Mobile that will make it easier to find out exactly what speeds you’re receiving on a throttled connection. The self-bred “uncarrier” will now send out a text message with a link to a test that accurately measures your throttled data rate.

T-Mobile also will change the language in the text message it already sends out to notify customers they’ve hit their limit. It will note that third-party speed tests won’t tell you how fast your current connection is, instead directing you to the T-Mobile test. The full details are available on the FCC’s site.

T-Mobile isn’t the only carrier to run afoul of the FCC in recent months. Earlier this year Verizon agreed to stop throttling customers on its unlimited data plans.

The impact on you: If you’re a T-Mobile customer, this will give you a better idea of how slow your newly-throttled connection is if you hit the limit. If you do it too often, maybe it’s time to upgrade to a better plan, especially with all of that data-free music streaming T-Mobile offers.