At some point along the way Xcode has consolidated the “Main Storyboard” and “Main Interface” fields pertaining to storyboard and nib files into a single “Main Interface” field that simply updates whichever of the pertinent Info.plist fields Xcode thinks you are working with.

The problem is that if you switch from storyboard to nib or back, then the value of the Info.plist entry is changed, but the key is not updated to reflect whether the new value is either a storyboard or a nib.

I’ve reported Radar 20954053 to Apple, requesting that Xcode should intuit from the file extension of the file named by “Main Interface” whether the Info.plist should advertise a storyboard or a nib.

In the mean time, if you switch from storyboard to nib or back, you need to manually update the Info.plist key to match: UIMainStoryboardFile if you’re using storyboards, or NSMainNibFile if you’re using nibs.