Labs ImageButton not showing image on iOS

I'm using an ImageButton, but it's not showing the associated image.

My image - football2-50.png - is in the resources folder and has a build action of BundledResource.

My code for creating the ImageButton is:

var imgGoals = new ImageButton { Source = "football2-50.png",
                ImageHeightRequest = 50,
                ImageWidthRequest = 50,
                Orientation = Xamarin.Forms.Labs.Enums.ImageOrientation.ImageToLeft,
                Text = "Goals"
            };

Is there something else I should be doing? I see previous posts referring to having to do something with ImageButtonRenderer in the AppDelegate. If this is the case, can someone give me details of what this entails?

I'm using Xamarin.Forms.Labs 1.2.1-pre2, and Xamarin.Forms 1.3.0.6275-pre1