diff --git a/content/svg/content/src/SVGDefsElement.cpp b/content/svg/content/src/SVGDefsElement.cpp
index 6d8226ae0a2a..91813e5984c1 100644
--- a/content/svg/content/src/SVGDefsElement.cpp
+++ b/content/svg/content/src/SVGDefsElement.cpp
@@ -6,8 +6,6 @@
 #include "mozilla/dom/SVGDefsElement.h"
 #include "mozilla/dom/SVGDefsElementBinding.h"
 
-DOMCI_NODE_DATA(SVGDefsElement, mozilla::dom::SVGDefsElement)
-
 NS_IMPL_NS_NEW_NAMESPACED_SVG_ELEMENT(Defs)
 
 namespace mozilla {
@@ -22,15 +20,9 @@ SVGDefsElement::WrapNode(JSContext *aCx, JSObject *aScope, bool *aTriedToWrap)
 //----------------------------------------------------------------------
 // nsISupports methods
 
-NS_IMPL_ADDREF_INHERITED(SVGDefsElement, SVGGraphicsElement)
-NS_IMPL_RELEASE_INHERITED(SVGDefsElement, SVGGraphicsElement)
-
-NS_INTERFACE_TABLE_HEAD(SVGDefsElement)
-  NS_NODE_INTERFACE_TABLE4(SVGDefsElement, nsIDOMNode, nsIDOMElement,
-                           nsIDOMSVGElement,
-                           nsIDOMSVGDefsElement)
-  NS_DOM_INTERFACE_MAP_ENTRY_CLASSINFO(SVGDefsElement)
-NS_INTERFACE_MAP_END_INHERITING(SVGGraphicsElement)
+NS_IMPL_ISUPPORTS_INHERITED3(SVGDefsElement, SVGGraphicsElement,
+                             nsIDOMNode, nsIDOMElement,
+                             nsIDOMSVGElement)
 
 //----------------------------------------------------------------------
 // Implementation
diff --git a/content/svg/content/src/SVGDefsElement.h b/content/svg/content/src/SVGDefsElement.h
index b373431d603a..34e646b71a4d 100644
--- a/content/svg/content/src/SVGDefsElement.h
+++ b/content/svg/content/src/SVGDefsElement.h
@@ -8,7 +8,6 @@
 
 #include "mozilla/Util.h"
 #include "SVGGraphicsElement.h"
-#include "nsIDOMSVGDefsElement.h"
 
 nsresult NS_NewSVGDefsElement(nsIContent **aResult,
                               already_AddRefed<nsINodeInfo> aNodeInfo);
@@ -17,7 +16,7 @@ namespace mozilla {
 namespace dom {
 
 class SVGDefsElement MOZ_FINAL : public SVGGraphicsElement,
-                                 public nsIDOMSVGDefsElement
+                                 public nsIDOMSVGElement
 {
 protected:
   friend nsresult (::NS_NewSVGDefsElement(nsIContent **aResult,
@@ -29,7 +28,6 @@ public:
   // interfaces:
 
   NS_DECL_ISUPPORTS_INHERITED
-  NS_DECL_NSIDOMSVGDEFSELEMENT
 
   // xxx I wish we could use virtual inheritance
   NS_FORWARD_NSIDOMNODE_TO_NSINODE
@@ -41,8 +39,6 @@ public:
 
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 
-  virtual nsXPCClassInfo* GetClassInfo();
-
   virtual nsIDOMNode* AsDOMNode() { return this; }
 };
 
diff --git a/dom/base/nsDOMClassInfo.cpp b/dom/base/nsDOMClassInfo.cpp
index 2b1984b68858..738a7f0599eb 100644
--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -319,7 +319,6 @@
 #include "nsIDOMSVGMpathElement.h"
 #include "nsIDOMTimeEvent.h"
 #include "nsIDOMSVGClipPathElement.h"
-#include "nsIDOMSVGDefsElement.h"
 #include "nsIDOMSVGDescElement.h"
 #include "nsIDOMSVGDocument.h"
 #include "nsIDOMSVGElement.h"
@@ -1071,8 +1070,6 @@ static nsDOMClassInfoData sClassInfoData[] = {
                            DOM_DEFAULT_SCRIPTABLE_FLAGS)
   NS_DEFINE_CLASSINFO_DATA(SVGClipPathElement, nsElementSH,
                            ELEMENT_SCRIPTABLE_FLAGS)
-  NS_DEFINE_CLASSINFO_DATA(SVGDefsElement, nsElementSH,
-                           ELEMENT_SCRIPTABLE_FLAGS)
   NS_DEFINE_CLASSINFO_DATA(SVGDescElement, nsElementSH,
                            ELEMENT_SCRIPTABLE_FLAGS)
   NS_DEFINE_CLASSINFO_DATA(SVGEllipseElement, nsElementSH,
@@ -3011,11 +3008,6 @@ nsDOMClassInfo::Init()
     DOM_CLASSINFO_SVG_GRAPHIC_ELEMENT_MAP_ENTRIES
   DOM_CLASSINFO_MAP_END
 
-  DOM_CLASSINFO_MAP_BEGIN(SVGDefsElement, nsIDOMSVGDefsElement)
-    DOM_CLASSINFO_MAP_ENTRY(nsIDOMSVGDefsElement)
-    DOM_CLASSINFO_SVG_GRAPHIC_ELEMENT_MAP_ENTRIES
-  DOM_CLASSINFO_MAP_END
-
   DOM_CLASSINFO_MAP_BEGIN(SVGDescElement, nsIDOMSVGDescElement)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMSVGDescElement)
     DOM_CLASSINFO_SVG_ELEMENT_MAP_ENTRIES
diff --git a/dom/base/nsDOMClassInfoClasses.h b/dom/base/nsDOMClassInfoClasses.h
index 4ed0389c8d67..e2cd026a3f45 100644
--- a/dom/base/nsDOMClassInfoClasses.h
+++ b/dom/base/nsDOMClassInfoClasses.h
@@ -195,7 +195,6 @@ DOMCI_CLASS(SVGAElement)
 DOMCI_CLASS(SVGMpathElement)
 DOMCI_CLASS(TimeEvent)
 DOMCI_CLASS(SVGClipPathElement)
-DOMCI_CLASS(SVGDefsElement)
 DOMCI_CLASS(SVGDescElement)
 DOMCI_CLASS(SVGEllipseElement)
 DOMCI_CLASS(SVGFEBlendElement)
diff --git a/dom/interfaces/svg/Makefile.in b/dom/interfaces/svg/Makefile.in
index fef2ec0dd0e9..2da755e2c457 100644
--- a/dom/interfaces/svg/Makefile.in
+++ b/dom/interfaces/svg/Makefile.in
@@ -25,7 +25,6 @@ XPIDLSRCS	= \
 		nsIDOMSVGAnimatedRect.idl \
 		nsIDOMSVGAnimatedString.idl \
 		nsIDOMSVGClipPathElement.idl \
-		nsIDOMSVGDefsElement.idl \
 		nsIDOMSVGDescElement.idl \
 		nsIDOMSVGDocument.idl \
 		nsIDOMSVGElement.idl \
diff --git a/dom/interfaces/svg/nsIDOMSVGDefsElement.idl b/dom/interfaces/svg/nsIDOMSVGDefsElement.idl
deleted file mode 100644
index b5a7a67e6a99..000000000000
--- a/dom/interfaces/svg/nsIDOMSVGDefsElement.idl
+++ /dev/null
@@ -1,28 +0,0 @@
-/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsIDOMSVGElement.idl"
-
-[scriptable, uuid(3F8D6B9C-CF03-45A6-B8A5-57ECBB7655DA)]
-interface nsIDOMSVGDefsElement
-  : nsIDOMSVGElement
-/*
-  The SVG DOM makes use of multiple interface inheritance.
-  Since XPCOM only supports single interface inheritance,
-  the best thing that we can do is to promise that whenever
-  an object implements _this_ interface it will also
-  implement the following interfaces. (We then have to QI to
-  hop between them.)
-  
-    nsIDOMSVGTests,
-    nsIDOMSVGLangSpace,
-    nsIDOMSVGExternalResourcesRequired,
-    nsIDOMSVGStylable,
-    nsIDOMSVGTransformable,
-    events::nsIDOMEventTarget
-*/
-{
-  
-};