mixing objective-c and swift when subclassing

I've got a subclass of UIViewController written in Swift called 'BaseViewController'. I now have an 'old' view controller called 'ViewController1' written in Objective-C that I want to inherit from 'BaseViewController'. Following other advice I have imported the 'Project-Swift.h' header file.

My problem occurs when subclassing like this

#import <UIKit/UIKit.h>
#import "MyProject-Swift.h"

@interface ViewController1 : BaseViewController
@end

The error is:

Cannot subclass a class with objc_subclassing-restricted attribute

and it appears on the @interface ... line.

You cannot subclass a Swift class in Objective-C.

Excerpt from Using Swift with Cocoa and Objective-C

You cannot subclass a Swift class in Objective-C. cf. towards the end of this section of the docs:

However, note that you cannot subclass a Swift class in Objective-C.