The FCC announced it has worked out an agreement with T-Mobile to ensure the carrier’s customers get accurate mobile broadband speed test readings even after they’ve been throttled.

T-Mobile last summer began exempting data speed tests from impacting customers’ data caps—similar to what the carrier does with streaming music—but speed tests under that program displayed full network speeds even if the customer is being throttled back to 128 Kbps or 64 Kbps.

T-Mobile offers unlimited data plans but reduced the speed of mobile broadband connections after customers use a certain amount of data. The FCC hopes the changes, which kick in immediately and will be fully implemented within 60 days, clarify actual performance.

“The FCC is committed to ensuring that broadband providers are transparent to consumers. I’m grateful T-Mobile has worked with the FCC to ensure that its customers are better informed about the speeds they are experiencing,” FCC Chairman Tom Wheeler said in a statement. “Consumers need this information to fully understand what they are getting with their broadband service.”

As part of the agreement T-Mobile will send customers a text message once they hit their monthly high-speed data allotment with a link to a reliable speed test and provide an on-device button linking to a speed test. The carrier will also modify the text messages it currently sends to customers after high-speed data allotments are exceeded to clarify that certain speed tests may not display throttled speeds and offer more information what kind of speeds are actually available after high-speed data allowances are exceeded.

The FCC this summer started issuing warnings to all four major U.S. carriers about throttling, which the Commission says led to Verizon canceling its plans to begin throttling 4G for its existing unlimited data customers.