Casting SKSpriteNode from .sks File to a Custom Class in iOS8

Hi All.

I've been experimenting with Xcode 7 and the updated SpriteKit Editor. For our current project we wish to design as much of the interface as possible visually. As there is no SKButton, I've created a simple Button class which extends SKSpriteNode

import SpriteKit

class Button: SKSpriteNode
{
    // MARK: Init
    init(texture: SKTexture, size: CGSize)
    {
        super.init(texture: texture, color: UIColor.whiteColor(), size: size)
        userInteractionEnabled = true
    }

    required init?(coder aDecoder: NSCoder)
    {
        super.init(coder: aDecoder)
        userInteractionEnabled = true
    }

    // MARK: User Interaction
    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?)
    {
        print("Button touchesBegan")
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?)
    {
        print("Button touchesMoved")
    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?)
    {
        print("Button touchesEnded")
    }

    override func touchesCancelled(touches: Set<UITouch>?, withEvent event: UIEvent?)
    {
        print("Button touchesCancelled")
    }
}

and a simple GameScene.sks file which contains a single, colored SKSpriteNode named button.

Now in GameScene.swift I can get a reference to this SKSpriteNode and cast it as a Button (regardless if a custom class is mentioned in the inspector panel or not).

let button = self.childNodeWithName("button") as! Button

Everything works perfectly fine when running on iOS 9, but on iOS 8 I receive the error

Could not cast value of type 'SKSpriteNode' to 'buttonTestProject.Button'

I am aware that the ability to assign a custom class in SpriteKit Editor is new in Xcode7, but the ability to cast a SKSpriteNode to a subclass surely isn't.

An ugly work-around is that the visual SKSpriteNode can be used as a placeholder to create a Button

let button: Button!
if #available(iOS 9, *)
{
  button = self.childNodeWithName("button") as! Button
}
else
{
  let node = self.childNodeWithName("button") as! SKSpriteNode
  button = Button(texture: node.texture!, size: node.size)
  button.position = node.position
  node.removeFromParent()
  addChild(button)
}

Any feedback would be greatly appreciated. I know that from the .sks file the NSCoder init method is called, but I don't see what could be different there for iOS 8. I suppose the issue is that Editor supports custom classes for iOS 9 onwards. Any alternative methods would be greatly appreciated also 😀 Thanks!