Brought the logic for handling isXMLDoc over from Sizzle.

diff --git a/src/core.js b/src/core.js
index 6dc4f00..13efaec 100644 (file)
--- a/src/core.js
+++ b/src/core.js
@@ -621,8 +621,8 @@ jQuery.extend({
 
        // check if an element is in a (or is an) XML document
        isXMLDoc: function( elem ) {
-               return elem.documentElement && !elem.body ||
-                       elem.tagName && elem.ownerDocument && !elem.ownerDocument.body;
+               return elem.nodeType === 9 && elem.documentElement.nodeName !== "HTML" ||
+                       !!elem.ownerDocument && jQuery.isXMLDoc( elem.ownerDocument );
        },
 
        // Evalulates a script in a global context