Apple this week acknowledged that a small batch of iPhone 5s devices include a problem that can affect the phone's battery life.
"We recently discovered a manufacturing issue affecting a very limited number of iPhone 5s devices that could cause the battery to take longer to charge or result in reduced battery life," Apple said in a statement. "We are reaching out to customers with affected phones and will provide them with a replacement phone."
Cupertino did not elaborate on just how many phones were affected.
On the Apple forums, there are several posts from 5s customers complaining about battery life, though it's not immediately clear if they are among those who are affected by this particular manufacturing issue.
"I noticed that the battery drains too fast on the 2 days old phone," one user wrote last week. "When i go to sleep i put alarm on, close all apps, switch off the sound, put the device in airplane mode. When i wake up, 8h, the battery drains 10% or more."
"I bought iphone 5-s on 25 October . I restored my phone from icloud backup but i noticed that my phone battery is draining so quickly even less than or [similar] to its predecessor iphone 5," another user wrote.
On the Apple website, the company says the 5s should get an average of 10 hours of talk time on 3G, up to 250 hours on standby, 8 hours of Internet use on 3G, and up to 10 hours on LTE and Wi-Fi. It should also have up to 10 hours of video playback and 40 hours on audio playback.
In the wake of the iOS 7 launch, there were also reports of battery drain for those who upgraded their old iPhones to the new mobile OS. The same thing happened in Nov. 2011, when Apple released an iOS 5 update that fixed a battery-draining bug.
For more, check out 7 Tips to Save iPhone Battery Life, as well as PCMag's full review of the iPhone 5s and the slideshow above.
Editor's Note: This story was updated at 10:55 a.m. ET.