     
     // MARK: Interface builder
     public override func prepareForInterfaceBuilder() {
+        super.prepareForInterfaceBuilder()
+        
         customInitialization()
     }
 }

public class CheckboxButton: UIButton {
    // MARK: Inspectable properties
    
    @IBInspectable public var checkLineWidth: CGFloat = 2.0 {
        didSet {
            layoutLayers()
        }
    }
    @IBInspectable public var checkColor: UIColor = UIColor.blackColor() {
        didSet {
            colorLayers()
        }
    }
    
    @IBInspectable public var containerLineWidth: CGFloat = 2.0 {
        didSet {
            layoutLayers()
        }
    }
    @IBInspectable public var containerColor: UIColor = UIColor.blackColor() {
        didSet {
            colorLayers()
        }
    }
    
    @IBInspectable public var circular: Bool = false {
        didSet {
            layoutLayers()
        }
    }
    @IBInspectable public var containerFillsOnSelected: Bool = false {
        didSet {
            colorLayers()

        customInitialization()
    }
    
    /**
     Initializes a new `CheckboxButton` with a selected state.
     
     - Parameters:
       - frame: Frame of the receiver
       - selected: Selected state of the receiver
    */
    convenience init(frame: CGRect, selected: Bool) {
        self.init(frame: frame)
        self.selected = selected
    }
    
    func customInitialization() {
        // Initial colors
        checkLayer.fillColor = UIColor.clearColor().CGColor
