Law enforcement officials have been warning each other that iPhones stored for forensic testing appear to be rebooting themselves — something security experts confirmed in a follow-up story. After rebooting, these phones become difficult to unlock with password-cracking tools, 404 Media reported Thursday.

This is not a defect in the phones, but probably a new feature released with the new operating system IOS 18.1, as this reboot occurs after phone have not been unlocked for a certain period of time. According to Chris Wade, founder of mobile analytics firm Corellium, iPhones seem to reboot after the fourth day of being locked.

Although it is considered a great improvement in the security, The company has not issued any statement confirming or denying this feature. But if it really exists, it may cause a clash and conflict with the police.