diff --git a/testing/marionette/element.js b/testing/marionette/element.js
index 807bfccc5aab..677153d5067e 100644
--- a/testing/marionette/element.js
+++ b/testing/marionette/element.js
@@ -34,7 +34,6 @@ const {
 
 const SVGNS = "http://www.w3.org/2000/svg";
 const XBLNS = "http://www.mozilla.org/xbl";
-const XHTMLNS = "http://www.w3.org/1999/xhtml";
 const XULNS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
 
 /** XUL elements that support checked property. */
@@ -1084,7 +1083,7 @@ element.isDOMElement = function(node) {
   return typeof node == "object" &&
       node !== null &&
       node.nodeType === node.ELEMENT_NODE &&
-      node.namespaceURI === XHTMLNS;
+      !element.isXULElement(node);
 };
 
 /**
diff --git a/testing/marionette/test_element.js b/testing/marionette/test_element.js
index ec2c8d37929c..4220a9c50cf8 100644
--- a/testing/marionette/test_element.js
+++ b/testing/marionette/test_element.js
@@ -138,7 +138,7 @@ add_test(function test_isElement() {
 
 add_test(function test_isDOMElement() {
   ok(element.isDOMElement(domEl));
-  ok(!element.isDOMElement(svgEl));
+  ok(element.isDOMElement(svgEl));
   ok(!element.isDOMElement(xulEl));
   ok(!element.isDOMElement(domWin));
   ok(!element.isDOMElement(domFrame));