Can't find interface declaration for my IOS view controller

I'm getting this error: "Cannot find interface declaration for 'BaseViewController', superclass of 'ViewController'. Here's the situation:

AppDelegate:

• Subclass of NSObject

• In the header file:

  #include UIApplicationDelegate

BaseViewController

• Subclass of UIViewController

• In the header file:

  #import "AppDelegate.h"

ViewController

• Subclass of BaseViewController

  #import "BaseViewController.h"

The error doesn't make sense, as BaseViewController is imported in ViewController's header file. What is the problem here?