Apple released a new update for the MacBook Pro with Touch Bar, giving the laptops a performance boost. (Photo courtesy of Apple) (Courtesy of Apple/Courtesy of Apple)

Apple fixed a software problem Tuesday that prevented its new MacBook Pro laptops from performing as well as promised.

The company said a problem with the part of the system that manages the temperature in laptops was mistakenly curtailing the processing speed of its newest MacBook Pros when owners pushed them to their limits. A fix for the bug is rolling out to all new MacBook Pro models.

Apple began selling the new laptops earlier this month, promising substantial performance improvements over previous models.

The trouble started for Apple when Dave Lee, a reviewer on YouTube, published a video July 18 in which he said that his testing showed that a model of the MacBook Pro with the highest-end i9 processor didn’t meet its benchmarks -- unless it was put in the freezer.

Lee identified the culprit as “thermal throttling,” a common occurrence in laptops in which computers will slow down performance to avoid getting too hot. But, Lee found, the MacBook Pro’s system kicked in far more often than it should have, slowing down so much in the test that the new computer was slower than its corresponding model from 2017.

“This degree of thermal throttling is not acceptable,” Lee said in his video. “This is not something that Apple should put out on the market.”

As Lee’s posts made the rounds, other Mac users said on Reddit that they’d had similar problems, with as least one person saying they’d returned their laptop as a result.

Richard Fisco, electronic testing leader at Consumer Reports, has not tested the laptops himself but said that Lee’s video certainly raised red flags. The MacBook Pro, he said, is a top-of-the-line laptop and should have been able to perform as advertised without throttling.

Apple has incorporated Lee’s tests into its own documentation and said in a statement that its original claims about its products should be true for all models with the fix in place.

“We apologize to any customer who has experienced less than optimal performance on their new systems,” Apple’s statement said.