diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index 6014b96e49c6..713bd60cbaa5 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -1537,7 +1537,6 @@ NS_INTERFACE_TABLE_HEAD(nsDocument)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIDOMDocumentTouch)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsITouchEventReceiver)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIInlineEventHandlers)
-    NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIDocumentRegister)
     NS_INTERFACE_TABLE_ENTRY(nsDocument, nsIObserver)
   NS_INTERFACE_TABLE_END
   NS_INTERFACE_TABLE_TO_MAP_SEGUE_CYCLE_COLLECTION(nsDocument)
@@ -5075,32 +5074,6 @@ nsDocument::RegisterEnabled()
   return sPrefValue;
 }
 
-NS_IMETHODIMP
-nsDocument::Register(const nsAString& aName, const JS::Value& aOptions,
-                     JSContext* aCx, uint8_t aOptionalArgc,
-                     jsval* aConstructor /* out param */)
-{
-  RootedDictionary<ElementRegistrationOptions> options(aCx);
-  if (aOptionalArgc > 0) {
-    JSAutoCompartment ac(aCx, GetWrapper());
-    JS::Rooted<JS::Value> opts(aCx, aOptions);
-    NS_ENSURE_TRUE(JS_WrapValue(aCx, opts.address()),
-                   NS_ERROR_UNEXPECTED);
-    NS_ENSURE_TRUE(options.Init(aCx, opts),
-                   NS_ERROR_UNEXPECTED);
-  }
-
-  ErrorResult rv;
-  JSObject* object = Register(aCx, aName, options, rv);
-  if (rv.Failed()) {
-    return rv.ErrorCode();
-  }
-  NS_ENSURE_TRUE(object, NS_ERROR_UNEXPECTED);
-
-  *aConstructor = OBJECT_TO_JSVAL(object);
-  return NS_OK;
-}
-
 JSObject*
 nsDocument::Register(JSContext* aCx, const nsAString& aName,
                      const ElementRegistrationOptions& aOptions,
diff --git a/content/base/src/nsDocument.h b/content/base/src/nsDocument.h
index fc960561824b..293abb01254a 100644
--- a/content/base/src/nsDocument.h
+++ b/content/base/src/nsDocument.h
@@ -60,7 +60,6 @@
 #include "nsIProgressEventSink.h"
 #include "nsISecurityEventSink.h"
 #include "nsIChannelEventSink.h"
-#include "nsIDocumentRegister.h"
 #include "imgIRequest.h"
 #include "mozilla/dom/DOMImplementation.h"
 #include "nsIDOMTouchEvent.h"
@@ -505,7 +504,6 @@ class nsDocument : public nsIDocument,
                    public nsStubMutationObserver,
                    public nsIDOMDocumentTouch,
                    public nsIInlineEventHandlers,
-                   public nsIDocumentRegister,
                    public nsIObserver
 {
 public:
@@ -796,9 +794,6 @@ public:
   // nsIInlineEventHandlers
   NS_DECL_NSIINLINEEVENTHANDLERS
 
-  // nsIDocumentRegister
-  NS_DECL_NSIDOCUMENTREGISTER
-
   // nsIObserver
   NS_DECL_NSIOBSERVER
 
diff --git a/dom/interfaces/core/moz.build b/dom/interfaces/core/moz.build
index 1c185e57de13..10f6ed014322 100644
--- a/dom/interfaces/core/moz.build
+++ b/dom/interfaces/core/moz.build
@@ -25,7 +25,6 @@ XPIDL_SOURCES += [
     'nsIDOMText.idl',
     'nsIDOMUserDataHandler.idl',
     'nsIDOMXMLDocument.idl',
-    'nsIDocumentRegister.idl',
     'nsIInlineEventHandlers.idl',
 ]
 
diff --git a/dom/interfaces/core/nsIDocumentRegister.idl b/dom/interfaces/core/nsIDocumentRegister.idl
deleted file mode 100644
index 701eb9936ba5..000000000000
--- a/dom/interfaces/core/nsIDocumentRegister.idl
+++ /dev/null
@@ -1,16 +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 "nsISupports.idl"
-
-[scriptable, uuid(e35935bd-ebae-4e0d-93bf-efa93ab14c05)]
-interface nsIDocumentRegister : nsISupports
-{
-  [optional_argc,
-   implicit_jscontext] jsval   register(in DOMString name,
-                                        [optional] in jsval options)
-                                 raises(DOMException);
-};
-