Apple’s (NSDQ:AAPL) latest iOS 8 operating system hit the market this week, but it’s missing one important piece: the HealthKit software.

The company has touting its foray into digital health and fitness, even calling HealthKit "the beginning of a health revolution," but iPhone users may not see much of that today. The iPhone update will still include the Health app for users, but the muscle behind it may be missing for a while.

The HealthKit bug has reportedly prevented 3rd-party developers from releasing their companion software, which powers the consumer-facing Health app. The HealthKit software package allows developers to transmit health and fitness data (collected with other programs and devices) with the Health app so that users can see data from multiple programs in a single silo.

Without HealthKit on the back end, the Health app may not have much to do. To its merit, the app itself "appeared to be functioning fine" at the time of release, PC World reported.

Apple told reporters that it expects to have HealthKit up and running by the end of the month.