Here is the full exception log (This happen when curl transition is set and we try to swipe up/down at first page) *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'The number of view controllers provided (0) doesn't match the number required (1) for the requested transition' *** First throw call stack: ( 0 CoreFoundation 0x00007ff8004ca369 __exceptionPreprocess + 242 1 libobjc.A.dylib 0x00007ff80008c106 objc_exception_throw + 62 2 CoreFoundation 0x00007ff8004ca247 -[NSException initWithCoder:] + 0 3 UIKitCore 0x00007ff80590b01c -[UIPageViewController _validatedViewControllersForTransitionWithViewControllers:animated:] + 538 4 UIKitCore 0x00007ff80590ba4c -[UIPageViewController _setViewControllers:withCurlOfType:fromLocation:direction:animated:notifyDelegate:completion:] + 599 5 UIKitCore 0x00007ff80590f16f -[UIPageViewController _handlePanGesture:] + 309 6 UIKitCore 0x00007ff805d57df0 -[UIGestureRecognizerTarget _sendActionWithGestureRecognizer:] + 71 7 UIKitCore 0x00007ff805d60e6b _UIGestureRecognizerSendTargetActions + 100 8 UIKitCore 0x00007ff805d5deb8 _UIGestureRecognizerSendActions + 306 9 UIKitCore 0x00007ff805d5db8e -[UIGestureRecognizer _updateGestureForActiveEvents] + 704 10 UIKitCore 0x00007ff805d4ff93 _UIGestureEnvironmentUpdate + 3892 11 CoreFoundation 0x00007ff8004289a4 CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 23 12 CoreFoundation 0x00007ff8004232f2 __CFRunLoopDoObservers + 534 13 CoreFoundation 0x00007ff800423814 __CFRunLoopRun + 1120 14 CoreFoundation 0x00007ff800422fb3 CFRunLoopRunSpecific + 536 15 GraphicsServices 0x00007ff8118c20cb GSEventRunModal + 137 16 UIKitCore 0x00007ff806400c3b -[UIApplication _run] + 875 17 UIKitCore 0x00007ff806405b7c UIApplicationMain + 123 18 Kobo Books.debug.dylib 0x00000001136300bb __debug_main_executable_dylib_entry_point + 75 19 dyld 0x000000010d702478 start_sim + 10 20 ??? 0x000000010fd9d345 0x0 + 4560900933 ) libc++abi: terminating due to uncaught exception of type NSException