diff --git a/dlls/mshtml/nsiface.idl b/dlls/mshtml/nsiface.idl
index fcdf6f1..3bbcd46 100644
--- a/dlls/mshtml/nsiface.idl
+++ b/dlls/mshtml/nsiface.idl
@@ -26,6 +26,7 @@
 cpp_quote("#define GECKO_VERSION \"2.21\"")
 cpp_quote("#define GECKO_VERSION_STRING \"Wine Gecko \" GECKO_VERSION")
 
+import "unknwn.idl";
 import "wtypes.idl";
 
 cpp_quote("#ifdef WINE_NO_UNICODE_MACROS")
@@ -114,12 +115,8 @@ interface IMoniker;
     uuid(00000000-0000-0000-c000-000000000046),
     local
 ]
-interface nsISupports
-{
-    nsresult QueryInterface(nsIIDRef riid, void **result);
-    nsrefcnt AddRef();
-    nsrefcnt Release();
-}
+interface nsISupports : IUnknown
+{}
 
 /* Currently we don't need a full declaration of these interfaces */
 typedef nsISupports nsISHistory;