Slight rendering issue on circles in text input

This is a bit of an esoteric issue and I'm probably only noticing it because I'm running osk-sdl on a desktop screen but I'm noticing a small rendering issue on the circles in the text input. The top right half seems to not be fully filled in white and the background is shining through along a small arc towards the edge.

If you zoom in on the area I framed in the screenshot above, you'll notice that the circle is not perfectly symmetric. The right half appears to be shifted up by one pixel compared to the left one. I'm not sure if that could maybe be related.