It seems like when we implement SVG sources for svg:image we didn't implement the overflow property (not sure about clip). See bug 272288 comment 36 SVG says that in such a case the overflow property on the root of the referenced SVG is ignored and the property on the image is used instead. See: http://www.w3.org/TR/SVG11/struct.html#ImageElement In the forthcoming test case the stroke of the referenced SVG is clipped since the viewBox of the image is sized to its geometric bounding box.

Test case demonstrating the issue. The stroke of the blue path is clipped despite the image being marked overflow:visible.