diff --git a/svg/interfaces.html b/svg/interfaces.html
index e5509ac58df7c4..83eccefcbf40a2 100644
--- a/svg/interfaces.html
+++ b/svg/interfaces.html
@@ -569,7 +569,7 @@
 };
 
 partial interface Document {
-  readonly attribute SVGSVGElement rootElement;
+  readonly attribute SVGSVGElement? rootElement;
 };
 
 interface SVGSVGElement : SVGGraphicsElement {