diff --git a/content/base/src/nsDOMAttribute.cpp b/content/base/src/nsDOMAttribute.cpp
index ddaa40ac6e38..4a02cd55c9ca 100644
--- a/content/base/src/nsDOMAttribute.cpp
+++ b/content/base/src/nsDOMAttribute.cpp
@@ -105,9 +105,9 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 // QueryInterface implementation for nsDOMAttribute
 NS_INTERFACE_TABLE_HEAD(nsDOMAttribute)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
-  NS_NODE_INTERFACE_TABLE7(nsDOMAttribute, nsIDOMAttr, nsIAttribute, nsINode,
+  NS_NODE_INTERFACE_TABLE8(nsDOMAttribute, nsIDOMAttr, nsIAttribute, nsINode,
                            nsIDOMNode, nsIDOM3Node, nsIDOM3Attr,
-                           nsPIDOMEventTarget)
+                           nsPIDOMEventTarget, nsIDOMXPathNSResolver)
   NS_INTERFACE_MAP_ENTRIES_CYCLE_COLLECTION(nsDOMAttribute)
   NS_INTERFACE_MAP_ENTRY_TEAROFF(nsISupportsWeakReference,
                                  new nsNodeSupportsWeakRefTearoff(this))
diff --git a/content/base/src/nsDOMAttribute.h b/content/base/src/nsDOMAttribute.h
index cac135e26cc9..a7b5bb61e33b 100644
--- a/content/base/src/nsDOMAttribute.h
+++ b/content/base/src/nsDOMAttribute.h
@@ -54,6 +54,7 @@
 #include "nsDOMAttributeMap.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsContentUtils.h"
+#include "nsIDOMXPathNSResolver.h"
 
 class nsDOMAttribute;
 
@@ -61,7 +62,8 @@ class nsDOMAttribute;
 // object that implements nsIDOMAttr, nsIDOM3Attr, nsIDOMNode, nsIDOM3Node
 class nsDOMAttribute : public nsIAttribute,
                        public nsIDOMAttr,
-                       public nsIDOM3Attr
+                       public nsIDOM3Attr,
+                       public nsIDOMXPathNSResolver
 {
 public:
   nsDOMAttribute(nsDOMAttributeMap* aAttrMap, nsINodeInfo *aNodeInfo,
diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index d0afa75447cc..da9dc2e04bca 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -1610,6 +1610,7 @@ NS_INTERFACE_TABLE_HEAD(nsDocument)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIMutationObserver)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIDOMNodeSelector)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIApplicationCacheContainer)
+    NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIDOMXPathNSResolver)
   NS_OFFSET_AND_INTERFACE_TABLE_END
   NS_OFFSET_AND_INTERFACE_TABLE_TO_MAP_SEGUE
   NS_INTERFACE_MAP_ENTRIES_CYCLE_COLLECTION(nsDocument)
diff --git a/content/base/src/nsDocument.h b/content/base/src/nsDocument.h
index f6d3c6c5885b..e19f21b29d2a 100644
--- a/content/base/src/nsDocument.h
+++ b/content/base/src/nsDocument.h
@@ -110,6 +110,7 @@
 #include "nsContentUtils.h"
 #include "nsThreadUtils.h"
 #include "nsIDocumentViewer.h"
+#include "nsIDOMXPathNSResolver.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsILoadContext.h"
 #include "nsIProgressEventSink.h"
@@ -573,6 +574,7 @@ class nsDocument : public nsIDocument,
                    public nsIRadioGroupContainer,
                    public nsIDOMNodeSelector,
                    public nsIApplicationCacheContainer,
+                   public nsIDOMXPathNSResolver,
                    public nsStubMutationObserver
 {
 public:
diff --git a/content/base/src/nsGenericDOMDataNode.cpp b/content/base/src/nsGenericDOMDataNode.cpp
index 1d59611e3bf9..774d2b8ea942 100644
--- a/content/base/src/nsGenericDOMDataNode.cpp
+++ b/content/base/src/nsGenericDOMDataNode.cpp
@@ -120,6 +120,8 @@ NS_INTERFACE_MAP_BEGIN(nsGenericDOMDataNode)
   NS_INTERFACE_MAP_ENTRY_TEAROFF(nsISupportsWeakReference,
                                  new nsNodeSupportsWeakRefTearoff(this))
   NS_INTERFACE_MAP_ENTRY_TEAROFF(nsIDOM3Node, new nsNode3Tearoff(this))
+  NS_INTERFACE_MAP_ENTRY_TEAROFF(nsIDOMXPathNSResolver,
+                                 new nsNode3Tearoff(this))
   // nsNodeSH::PreCreate() depends on the identity pointer being the
   // same as nsINode (which nsIContent inherits), so if you change the
   // below line, make sure nsNodeSH::PreCreate() still does the right
diff --git a/content/base/src/nsGenericElement.cpp b/content/base/src/nsGenericElement.cpp
index a695a13d864a..41743f56a651 100644
--- a/content/base/src/nsGenericElement.cpp
+++ b/content/base/src/nsGenericElement.cpp
@@ -636,6 +636,7 @@ NS_IMPL_CYCLE_COLLECTION_1(nsNode3Tearoff, mContent)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsNode3Tearoff)
   NS_INTERFACE_MAP_ENTRY(nsIDOM3Node)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMXPathNSResolver)
 NS_INTERFACE_MAP_END_AGGREGATED(mContent)
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(nsNode3Tearoff)
@@ -856,7 +857,8 @@ nsNode3Tearoff::GetFeature(const nsAString& aFeature,
                            const nsAString& aVersion,
                            nsISupports** aReturn)
 {
-  return nsGenericElement::InternalGetFeature(this, aFeature, aVersion, aReturn);
+  return nsGenericElement::InternalGetFeature(static_cast<nsIDOM3Node*>(this),
+                                              aFeature, aVersion, aReturn);
 }
 
 NS_IMETHODIMP
@@ -4078,6 +4080,8 @@ NS_INTERFACE_MAP_BEGIN(nsGenericElement)
                                  new nsNodeSupportsWeakRefTearoff(this))
   NS_INTERFACE_MAP_ENTRY_TEAROFF(nsIDOMNodeSelector,
                                  new nsNodeSelectorTearoff(this))
+  NS_INTERFACE_MAP_ENTRY_TEAROFF(nsIDOMXPathNSResolver,
+                                 new nsNode3Tearoff(this))
   // nsNodeSH::PreCreate() depends on the identity pointer being the
   // same as nsINode (which nsIContent inherits), so if you change the
   // below line, make sure nsNodeSH::PreCreate() still does the right
diff --git a/content/base/src/nsGenericElement.h b/content/base/src/nsGenericElement.h
index dcd60851a40c..a115addc2cfb 100644
--- a/content/base/src/nsGenericElement.h
+++ b/content/base/src/nsGenericElement.h
@@ -64,6 +64,7 @@
 #include "nsCycleCollectionParticipant.h"
 #include "nsIDocument.h"
 #include "nsIDOMNodeSelector.h"
+#include "nsIDOMXPathNSResolver.h"
 
 #ifdef MOZ_SMIL
 #include "nsISMILAttr.h"
@@ -144,14 +145,14 @@ private:
 /**
  * A tearoff class for nsGenericElement to implement additional interfaces
  */
-class nsNode3Tearoff : public nsIDOM3Node
+class nsNode3Tearoff : public nsIDOM3Node, public nsIDOMXPathNSResolver
 {
 public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
 
   NS_DECL_NSIDOM3NODE
 
-  NS_DECL_CYCLE_COLLECTION_CLASS(nsNode3Tearoff)
+  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(nsNode3Tearoff, nsIDOM3Node)
 
   nsNode3Tearoff(nsIContent *aContent) : mContent(aContent)
   {
diff --git a/content/base/test/Makefile.in b/content/base/test/Makefile.in
index c0eb7da91b31..15099885ceca 100644
--- a/content/base/test/Makefile.in
+++ b/content/base/test/Makefile.in
@@ -129,6 +129,7 @@ _TEST_FILES = 	test_bug5141.html \
 		test_bug382113.html \
 		test_bug382871.html \
 		test_bug383430.html \
+		test_bug384003.xhtml \
 		test_bug390219.html \
 		test_bug390735.html \
 		test_bug392318.html \
diff --git a/content/base/test/test_bug384003.xhtml b/content/base/test/test_bug384003.xhtml
new file mode 100644
index 000000000000..d5250f5e3753
--- /dev/null
+++ b/content/base/test/test_bug384003.xhtml
@@ -0,0 +1,86 @@
+<?xml version="1.0"?>
+<html xmlns="http://www.w3.org/1999/xhtml" attr="value">
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=384003
+-->
+<head>
+  <title>Test for Bug 384003</title>
+  <script type="application/javascript" src="/MochiKit/packed.js"></script>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=384003">Mozilla Bug 384003</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+  
+</div>
+<pre id="test" xmlns:foo="http://www.foo.org"><foo:foo/>
+<script type="application/javascript">
+<![CDATA[
+
+/** Test for Bug 384003 **/
+
+
+function resolverTest(expr, resolver, result, extype) {
+  if (!extype) {
+    extype = 0;
+  }
+  try {
+    is(document.evaluate(expr, document, resolver,
+                         XPathResult.FIRST_ORDERED_NODE_TYPE, null).
+                           singleNodeValue,
+                         result,
+                         "Wrong XPathResult");
+    if (extype) {
+      ok(false, "Should have got an exception!");
+    }
+  } catch(ex) {
+    is(ex.code, extype, "Wrong exception");
+  }
+}
+
+// Expression should return document element.
+// Document resolver
+resolverTest("*", document, document.documentElement);
+// Element resolver
+resolverTest("*", document.documentElement, document.documentElement);
+// Attribute resolver
+resolverTest("*", document.documentElement.getAttributeNode("attr"),
+             document.documentElement);
+// Text node resolver
+resolverTest("*", document.documentElement.firstChild,
+             document.documentElement);
+// Comment node resolver
+resolverTest("*", document.documentElement.firstChild.nextSibling,
+             document.documentElement);
+
+// Expression should return foo element, but because of the
+// resolver it may throw an exception.
+var NAMESPACE_ERR = 14;
+var foo = document.getElementById("test").firstChild;
+// Document resolver
+resolverTest("//foo:foo", document, foo, NAMESPACE_ERR);
+// Element resolver
+resolverTest("//foo:foo", document.documentElement, foo, NAMESPACE_ERR);
+// Attribute resolver
+resolverTest("//foo:foo", document.documentElement.getAttributeNode("attr"),
+             foo, NAMESPACE_ERR);
+// Text node resolver
+resolverTest("//foo:foo", document.documentElement.firstChild,
+             foo, NAMESPACE_ERR);
+// Comment node resolver
+resolverTest("//foo:foo", document.documentElement.firstChild.nextSibling,
+             foo, NAMESPACE_ERR);
+// Function resolver
+resolverTest("//foo:foo",
+             function(p) { return (p == "foo") ? "http://www.foo.org" : ""; },
+             foo);
+// Element resolver, which has definition for foo namespace
+resolverTest("//foo:foo", foo.parentNode, foo);
+
+]]>
+</script>
+</pre>
+</body>
+</html>