Webkit button: color overflows round corners

Question

I'm trying to make a rounded button using -webkit-border-radius

This gives me this button (in Safari):

You can see that the color overflows in the rounding. I tried changing border size and radius, and it doesn't help. Is this a rendering bug with Safari or something?

Answer 1

Looks like this is a rendering bug with WebKit. Adam Betts on Twitter:

We're at Safari 5 and border-radius artifacts is still here. Why isn't this fixed already? http://lensco.be/test/border-radius-artifacts/