--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -1029,17 +1029,17 @@ nsHTMLDocument::SetBody(nsIDOMHTMLElemen
   ErrorResult rv;
   SetBody(static_cast<nsGenericHTMLElement*>(newBody.get()), rv);
   return rv.StealNSResult();
 }
 
 void
 nsHTMLDocument::SetBody(nsGenericHTMLElement* newBody, ErrorResult& rv)
 {
-  Element* root = GetRootElement();
+  nsCOMPtr<Element> root = GetRootElement();
 
   // The body element must be either a body tag or a frameset tag. And we must
   // have a html root tag, otherwise GetBody will not return the newly set
   // body.
   if (!newBody ||
       !newBody->IsAnyOfHTMLElements(nsGkAtoms::body, nsGkAtoms::frameset) ||
       !root || !root->IsHTMLElement() ||
       !root->IsHTMLElement(nsGkAtoms::html)) {