Creating a proxy of an object and casting it as the object's type

Using Swift
,
3

I managed to create a NSProxy subclass in Objective-C that can be casted as its object type.

@interface ObjectProxy : NSProxy
@property (nonatomic, strong) id target;
- (instancetype)initWithTarget:(id)target;
@end

@implementation ObjectProxy

- (instancetype)initWithTarget:(id)target {
    _target = target;
    return self;
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
    return [_target methodSignatureForSelector:sel];
}

- (void)forwardInvocation:(NSInvocation *)invocation {
    [invocation setTarget:_target];
    [invocation invoke];
}
@end

In Swift I can use:

let myObject = MyObject()
let proxy = ObjectProxy(target: myObject)
let proxiedObject = proxy as? MyObject

Problem: When I use any subclass I created as target, I can't cast the proxy to the subclass type and only to the object type I subclassed:

class CustomView: NSView {  }

let view = CustomView()
let proxy = ObjectProxy(target: view)
proxy as? CustomView // Fails
proxy as? NSView // Works

However casting a proxy of a subclass I create in Objective-C works:

@interface CustomView : NSView
@end

@implementation CustomView
@end

// Swift
let view = CustomView()
let proxy = ObjectProxy(target: view)
proxy as? CustomView // Works

I found this NSProxy dynamic casting to Swift or ObjC class behaves differently, but I'm unsure if it's related.