Amid all of the excitement during this weekend’s iPhone 15 launch, some early buyers took to social media to complain about overheating handsets that were affecting comfort and performance. While most people assumed it was due to the A17 Pro processor, a new report suggests that might not be the case.

According to analyst Ming-Chi Kuo, the iPhone 15 Pro’s overheating issues are “unrelated to TSMC’s advanced 3nm node,” the new process Apple is using for the breakthrough A17 Pro processor. Rather, Kuo explains, the overheating issue is likely caused by “the compromises made in the thermal system design to achieve a lighter weight, such as the reduced heat dissipation area and the use of a titanium frame, which negatively impacts thermal efficiency.”

The iPhone 15 Pro models have dramatically reduced weight, with the Pro Max losing some 20 grams and feeling much lighter than the iPhone 14 Pro Max. However, Apple made some internal changes as well that have apparently affected the cooling of the chip.

Kuo says Apple is expected to address the overheating issues in a software update, though he cautions that “improvements may be limited unless Apple lowers processor performance.” It will likely be several weeks before such a fix is implemented as Apple hasn’t started beta testing iOS 17.1 yet.

In our testing, we also found our iPhone 15 Pro Max to overheat during charging, an issue that has also been fairly widespread among early adopters. The iPhone 15 has a USB-C charging/data port for the first time after using Lightning for the past 10 years. Kuo doesn’t mention whether Apple is investigating this particular issue.