I have a poly curve which makes a square, so the thickness of the curve remains constant. When I move one of the handles downwards, elongating the shape, the thickness of the curve changes:

[![enter image description here](https://i.stack.imgur.com/5DsBy.png)](https://i.stack.imgur.com/5DsBy.png)

Is there a way to maintain the thickness of the curve automatically? I've found I can subdivide the sides and then move the resulting points very close to but not at the downmost vertex to achieve what I want, but that feels a bit weird.