diff --git a/content/html/content/src/HTMLSharedElement.cpp b/content/html/content/src/HTMLSharedElement.cpp
index 6b2c6d99591d..34196a8bab72 100644
--- a/content/html/content/src/HTMLSharedElement.cpp
+++ b/content/html/content/src/HTMLSharedElement.cpp
@@ -53,9 +53,6 @@ NS_IMPL_STRING_ATTR(HTMLSharedElement, Type, type)
 NS_IMPL_STRING_ATTR(HTMLSharedElement, Value, value)
 NS_IMPL_STRING_ATTR(HTMLSharedElement, ValueType, valuetype)
 
-// nsIDOMHTMLDirectoryElement
-NS_IMPL_BOOL_ATTR(HTMLSharedElement, Compact, compact)
-
 // nsIDOMHTMLQuoteElement
 NS_IMPL_URI_ATTR(HTMLSharedElement, Cite, cite)
 
diff --git a/content/html/content/src/HTMLSharedElement.h b/content/html/content/src/HTMLSharedElement.h
index c18dbc88cb27..75e892161ed2 100644
--- a/content/html/content/src/HTMLSharedElement.h
+++ b/content/html/content/src/HTMLSharedElement.h
@@ -55,9 +55,6 @@ public:
   // nsIDOMHTMLBaseElement
   NS_DECL_NSIDOMHTMLBASEELEMENT
 
-  // nsIDOMHTMLDirectoryElement
-  NS_DECL_NSIDOMHTMLDIRECTORYELEMENT
-
   // nsIDOMHTMLQuoteElement
   NS_DECL_NSIDOMHTMLQUOTEELEMENT
 
diff --git a/dom/interfaces/html/nsIDOMHTMLDirectoryElement.idl b/dom/interfaces/html/nsIDOMHTMLDirectoryElement.idl
index f68cc0d0cac7..ec9670861071 100644
--- a/dom/interfaces/html/nsIDOMHTMLDirectoryElement.idl
+++ b/dom/interfaces/html/nsIDOMHTMLDirectoryElement.idl
@@ -16,8 +16,8 @@
  * http://www.whatwg.org/specs/web-apps/current-work/
  */
 
+// Exists so that | element instanceof Ci.nsIDOMHTMLDirectoryElement | works.
 [scriptable, uuid(cf50373e-e004-4cec-bc65-be9250d9e4c8)]
 interface nsIDOMHTMLDirectoryElement : nsIDOMHTMLElement
 {
-           attribute boolean          compact;
 };