diff --git a/dom/webidl/Element.webidl b/dom/webidl/Element.webidl
index 7163fac826..c0c201e29d 100644
--- a/dom/webidl/Element.webidl
+++ b/dom/webidl/Element.webidl
@@ -288,6 +288,9 @@ partial interface Element {
   [BinaryName="shadowRootByMode"]
   readonly attribute ShadowRoot? shadowRoot;
 
+  [Func="Document::IsCallerChromeOrAddon", BinaryName="shadowRoot"]
+  readonly attribute ShadowRoot? shadowRootUnl;
+
   [Func="Document::IsCallerChromeOrAddon", BinaryName="shadowRoot"]
   readonly attribute ShadowRoot? openOrClosedShadowRoot;