Eager to try out Apple's second-generation smartwatch operating system? You're going to have to wait a little longer.

According to Reuters, Apple won't be releasing watchOS 2 today, as originally planned, due to a bug discovered during development. The flaw is reportedly taking a little longer to fix than Apple expected.

"We will not release watchOS 2 today but will shortly," a spokeswoman told Reuters.

Apple did not immediately respond to a request for comment.

Apple last week announced plans to release watchOS 2 as a free upgrade on Sept. 16. The new operating system "makes apps faster and more fluid by running natively on Apple Watch," and brings some new watch faces along with the ability for third-party apps to display information on the watch face. A new feature called Time Travel lets you easily scroll through upcoming events. You'll also be able to more quickly respond to Mail with dictation, Smart Replies, or emojis.

PCMag's Sascha Segan got some hands-on time with the new watch software at Apple's iPhone launch event last week, and said it "makes the watch even more fashionable, but it doesn't solve the utility question."

"I can only understand the Watch as a fashion item," Segan concluded. "It's an elegant design statement that has some useful technology features, not a life-changing piece of technology that happens to have some style."

Meanwhile, Apple last week expanded its Apple Watch lineup with a number of new case and band options, including gold and rose gold aluminum sport models.

For more on watchOS2, check out the video below. Also be sure to see our full review of the Apple Watch.

In the meantime, you can download iOS 9, which did arrive today as scheduled. For more, check out 13 Intriguing Features in Apple's iOS 9.