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

        customInitialization()
    }
    
    func customInitialization() {
        // Initial colors
        checkLayer.fillColor = UIColor.clearColor().CGColor

public class CheckboxButton: UIButton {
    // MARK: Inspectable properties
    
    /// Line width for the check mark. Default value is 2.
    @IBInspectable public var checkLineWidth: CGFloat = 2.0 {
        didSet {
            layoutLayers()
        }
    }
    
    /// Color for the check mark. Default color is `UIColor.blackColor()`.
    @IBInspectable public var checkColor: UIColor = UIColor.blackColor() {
        didSet {
            colorLayers()
        }
    }
    
    /// Line width for the bounding container of the check mark.
    /// Default value is 2.
    @IBInspectable public var containerLineWidth: CGFloat = 2.0 {
        didSet {
            layoutLayers()
        }
    }
    
    /// Color for the bounding container of the check mark.
    /// Default color is `UIColor.blackColor()`.
    @IBInspectable public var containerColor: UIColor = UIColor.blackColor() {
        didSet {
            colorLayers()
        }
    }
    
    /// If set to `true`, the bounding container of the check mark will be a circle rather than a box.
    /// Default value is false
    @IBInspectable public var circular: Bool = false {
        didSet {
            layoutLayers()
        }
    }
    
    /// If set to `true`, the container gets a fill color similar to the `containerColor` property.
    /// Default value is `false`.
    @IBInspectable public var containerFillsOnSelected: Bool = false {
        didSet {
            colorLayers()
