No expections, all works fine

<?xml version="1.0" standalone="no"?>
<svg width="200" height="200" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1">
    <defs>
        <pattern id="p1" x=".05" y=".05" width=".15" height=".15">
            <rect x="0" y="0" width="20" height="20" fill="skyblue"/>
        </pattern>
        <pattern id="p2" width=".35" xlink:href="#p1">
            <rect x="0" y="0" width="30" height="20" fill="green"/>
        </pattern>
    </defs>
    <rect fill="url(#p2)" stroke="black" x="0" y="0" width="200" height="200"/>
</svg>