[pygame] left-over pixels in pygame.draw.circle?

["Hugo Arts" <hugo.yoshi@xxxxxxxxx>]

I've been getting strange results in pygame.draw.circle and pygame.draw.arc:
if I specify a (non-zero) width for the circle/arc the resulting image is not drawn properly.
A strange pattern of pixels remains its previous color on the target surface. This does not occur if I completely fill the circle/arc

I've put up an image that might explain things more clearly. It is the pygame window resulting from this code:

>>> import pygame
>>> screen = pygame.display.set_mode((100, 100))
>>> pygame.draw.circle(screen, (255, 255, 255), (50, 50), 40, 20)
<rect(30, 30, 40, 40)>
>>> pygame.display.update()

here's the link to the image: http://img355.imageshack.us/img355/3488/circlehh4.png

I tried this both on 1.7.1 and 1.8.0 (I was still running 1.7.1, thought that upgrading might fix it), and it happens on both versions.
I am running this on a Linux box.