Xamarin RadioButton.Content not showing correct content

I'm trying to set an image inside a RadioButton like shown at https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/radiobutton

<RadioButton>
    <RadioButton.Content>
        <Image Source="icon.png"/>
    </RadioButton.Content>
</RadioButton>

But in app it shows only the text "Xamarin.Forms.Image" instead of the image.

What is wrong? I just did it like in the example.