Apple is holding off on offering an update to its Apple Watch operating system due to a software bug.

watchOS 2 was due today (Sept. 16) alongside iOS 9, but instead will be delivered ‘shortly’.

It’s a smart move on Apple’s part. When it released iOS 8 last September, the software contained bugs that affected Wi-Fi, TouchID and some other parts of iOS.

Apple released a statement on the delay, but didn’t get specific on either when it wold be launched, or what the bug was: “We have discovered a bug in development of Watch OS 2 that is taking a bit longer to fix than we expected. We will not release Watch OS 2 today but will shortly.”

iOS 9 on the other hand, arrived as planned and is now available for iPhone, iPad and iPod Touch users. Read more about the launch of iOS 9.

Read more: What’s coming in watchOS 2