BorderRadius differences between Android and iOS

Hi,

I'm using borderRadius to turn my square images to circles an example of how i'm doing this is:

"#avatar":{
    top: 20,
    width: 100,
    height: 100,
    borderRadius: 50,
    borderWidth: 5
}

I'm setting the borderRadius to half the width which works perfectly on iOS and makes it a perfect circle, however on android this does not seem to make it a circle just rounds the corners and it looks different on different devices, is there a way to achieve this effect on android?