Google Chrome: 6.0.472.25 dev Safari/Webkit: Version 5.0.1 (6533.17.8, r63640) I have a foreignObject in a <defs> and cannot apply a mask to it, because the foreignObject keeps getting rendered fully. Here is the example: <?xml version="1.0"?> <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" height="270px" width="480px"> <mask id="c1" maskUnits="userSpaceOnUse" maskContentUnits="userSpaceOnUse"> <circle id="circle" cx="240" cy="135" r="135" fill="white"/> </mask> <defs> <g id="videoGroup"> <foreignObject width="100%" height="100%"> <body xmlns="http://www.w3.org/1999/xhtml"> <video id="vid" class="target" height="270px" width="480px" controls="controls" autoplay="autoplay"> <source src="http://annodex.net/~silvia/itext/chocolate_rain/chocolate_rain.mp4" type="video/mp4"/> <source src="http://annodex.net/~silvia/itext/chocolate_rain/chocolate_rain.ogv" type="video/ogg"/> </video> </body> </foreignObject> </g> </defs> <use xlink:href="#videoGroup" mask="url(#c1)"/> </svg>