Back button is not visible in iOS 7

Question

I have some weird trouble about iOS 7. I have an UINavigationBar in my app and it works perfect for iOS 6;

-- IOS 6 --

Answer 1

I used Wes Dearborn's answer and implemented a nice way of supporting both iOS5+'s back button and iOS7's backIndicatorImage:

Back button strangely disappearing in UINavigationController but keeps working