When A UIPageViewController is used inside a UINavigationController constraints in the managed view controllers related to the top layout guide are setup/updated to late. They should be update in viewWillAppear, before any part of the shown pages  is first displayed. Instead the constraints are only updated on what appear to be viewDidAppear: or a similar method. At least, the constraints are only correct after the page view controller’s animation finished, not during the animation of a newly loaded child view controller.