When I apply a border image to an input[type="submit"] element it seems to behave as if the border width is set to zero, ignoring the values set. This only happens in IE9. The same code works fine in older browsers, and when applied to other element types.

I found a workaround of adding !important to my border widths. It would appear that PIE is incorrectly resetting this property.

This didn't work - it screwed up other IE versions. I did however find a solution by editing the source, which I've posted alongside a bug report in Github.

Thanks for the GitHub ticket and analysis, I will investigate this and make sure the proposed fix is safe.