Border around video isn't scaling into a perfect square

So I am trying to create a boarder on my video by creating a shape layer using the rectange tool and then setting it to no fill and bringing the stroke width up. Although, when I scale the stroke width up it doesn't create a perfect square around my video (which is 1080x1080). I tried aligning it and that didn't work either. I'm using square pixels as well so I don't know why it's not scaling correctly.