I'm trying to make a circular border within a PhysicalModel. It works if I don't wrap my widget in a PhysicalModel, but once I do, I get a square-ish border.

```
new PhysicalModel(
  color: Colors.green,
  child: new Container(
    width: 50.0,
    height: 50.0,
    decoration: new BoxDecoration(
      borderRadius: new BorderRadius.circular(25.0),
      border: new Border.all(
        width: 5.0,
        color: Colors.red,
      ),
    ),
  ),
),

```