Apple’s iPhone battery replacement program could cause the company to lose out on millions of new iPhone sales, according to analysts at Barclays.

It was revealed last month that the company intentionally throttles CPU speeds on some iPhones with older batteries to provide an overall better experience. Apple has offered $29 battery replacements to make up for it, but that might be bad news for its bottom line.

Barclays analyst Mark Moskowitz estimates that the program might cause up to 16 million iPhone owners to wait to upgrade. Given that iPhone makes up nearly two-thirds of Apple’s revenues, investors aren’t too keen to see even a small dip in upgrade percentage.

“Even a small percentage [of customers] opting for battery replacement over upgrade could have meaningful impact on iPhone sales,” Moskowitz wrote in a note to investors obtained by Bloomberg.

Battery replacement fees on the iPhone typically cost $79. Now that Apple has lowered the price to just $29 for all of 2018, owners of the iPhone 6s and later can get a cheap speed boost by swapping in a new battery.

In its apology letter to customers, Apple revealed that it added a feature to an iOS 10 update that lowered CPU demands on older batteries. This was added as a way to prevent unwanted random reboots from occurring when the CPU drew more power than the old battery could support.

Although a fresh battery could make some users hold onto their old devices for longer, new features on the latest iPhones will could lure them to upgrade anyway.