diff --git a/include/oleacc.idl b/include/oleacc.idl
index dc7af158193..9edfdda7763 100644
--- a/include/oleacc.idl
+++ b/include/oleacc.idl
@@ -154,10 +154,11 @@ typedef enum AnnoScope
 } AnnoScope;
 
 [
-  local,
-  object,
-  uuid(618736e0-3c3d-11cf-810c-00aa00389b71),
-  pointer_default(unique)
+    object,
+    hidden,
+    dual,
+    uuid(618736e0-3c3d-11cf-810c-00aa00389b71),
+    pointer_default(unique)
 ]
 interface IAccessible : IDispatch
 {
@@ -185,26 +186,26 @@ interface IAccessible : IDispatch
     [hidden, propget, id(DISPID_ACC_PARENT)] HRESULT accParent([out, retval]IDispatch** ppdispParent);
     [hidden, propget, id(DISPID_ACC_CHILDCOUNT)] HRESULT accChildCount([out, retval] long* pcountChildren);
     [hidden, propget, id(DISPID_ACC_CHILD)] HRESULT accChild([in] VARIANT varChildID, [out, retval]IDispatch **ppdispChild);
-    [hidden, propget, id(DISPID_ACC_NAME)] HRESULT accName([in]VARIANT varID, [out, retval] BSTR* pszName);
-    [hidden, propget, id(DISPID_ACC_VALUE)] HRESULT accValue([in]VARIANT varID, [out, retval] BSTR* pszValue);
-    [hidden, propget, id(DISPID_ACC_DESCRIPTION)] HRESULT accDescription([in]VARIANT varID, [out, retval] BSTR* pszDescription);
-    [hidden, propget, id(DISPID_ACC_ROLE)] HRESULT accRole([in]VARIANT varID, [out, retval]VARIANT* pvarRole);
-    [hidden, propget, id(DISPID_ACC_STATE)] HRESULT accState([in]VARIANT varID, [out, retval]VARIANT* pvarState);
-    [hidden, propget, id(DISPID_ACC_HELP)] HRESULT accHelp([in]VARIANT varID, [out, retval]BSTR* pszHelp);
-    [hidden, propget, id(DISPID_ACC_HELPTOPIC)] HRESULT accHelpTopic([out]BSTR* pszHelpFile, [in]VARIANT varID, [out, retval] long* pidTopic);
-    [hidden, propget, id(DISPID_ACC_KEYBOARDSHORTCUT)] HRESULT accKeyboardShortcut([in]VARIANT varID, [out, retval] BSTR* pszKeyboardShortcut);
+    [hidden, propget, id(DISPID_ACC_NAME)] HRESULT accName([in, optional] VARIANT varID, [out, retval] BSTR* pszName);
+    [hidden, propget, id(DISPID_ACC_VALUE)] HRESULT accValue([in, optional] VARIANT varID, [out, retval] BSTR* pszValue);
+    [hidden, propget, id(DISPID_ACC_DESCRIPTION)] HRESULT accDescription([in, optional] VARIANT varID, [out, retval] BSTR *description);
+    [hidden, propget, id(DISPID_ACC_ROLE)] HRESULT accRole([in, optional] VARIANT varID, [out, retval] VARIANT *role);
+    [hidden, propget, id(DISPID_ACC_STATE)] HRESULT accState([in, optional] VARIANT varID, [out, retval] VARIANT *state);
+    [hidden, propget, id(DISPID_ACC_HELP)] HRESULT accHelp([in, optional] VARIANT varID, [out, retval] BSTR *help);
+    [hidden, propget, id(DISPID_ACC_HELPTOPIC)] HRESULT accHelpTopic([out] BSTR *helpfile, [in, optional] VARIANT varID, [out, retval] long* pidTopic);
+    [hidden, propget, id(DISPID_ACC_KEYBOARDSHORTCUT)] HRESULT accKeyboardShortcut([in, optional] VARIANT varID, [out, retval] BSTR *shortcut);
     [hidden, propget, id(DISPID_ACC_FOCUS)] HRESULT accFocus([out, retval] VARIANT* pvarID);
     [hidden, propget, id(DISPID_ACC_SELECTION)] HRESULT accSelection([out, retval] VARIANT* pvarID);
-    [hidden, propget, id(DISPID_ACC_DEFAULTACTION)] HRESULT accDefaultAction([in]VARIANT varID, [out, retval] BSTR* pszDefaultAction);
+    [hidden, propget, id(DISPID_ACC_DEFAULTACTION)] HRESULT accDefaultAction([in, optional] VARIANT varID, [out, retval] BSTR *action);
 
-    [hidden, id(DISPID_ACC_SELECT)] HRESULT accSelect([in]long flagsSelect, [in]VARIANT varID);
-    [hidden, id(DISPID_ACC_LOCATION)] HRESULT accLocation([out]long* pxLeft, [out]long* pyTop, [out]long* pcxWidth, [out]long* pcyHeight, [in]VARIANT varID);
-    [hidden, id(DISPID_ACC_NAVIGATE)] HRESULT accNavigate([in]long navDir, [in]VARIANT varStart, [out, retval] VARIANT* pvarEnd);
-    [hidden, id(DISPID_ACC_HITTEST)] HRESULT accHitTest([in]long xLeft, [in]long yTop, [out,retval] VARIANT* pvarID);
-    [hidden, id(DISPID_ACC_DODEFAULTACTION)] HRESULT accDoDefaultAction([in]VARIANT varID);
+    [hidden, id(DISPID_ACC_SELECT)] HRESULT accSelect([in] long flagsSelect, [in, optional] VARIANT varID);
+    [hidden, id(DISPID_ACC_LOCATION)] HRESULT accLocation([out] long *left, [out] long *top, [out] long *width, [out] long *height, [in, optional] VARIANT varID);
+    [hidden, id(DISPID_ACC_NAVIGATE)] HRESULT accNavigate([in] long dir, [in, optional] VARIANT varStart, [out, retval] VARIANT *pvarEnd);
+    [hidden, id(DISPID_ACC_HITTEST)] HRESULT accHitTest([in] long left, [in] long top, [out, retval] VARIANT *pvarID);
+    [hidden, id(DISPID_ACC_DODEFAULTACTION)] HRESULT accDoDefaultAction([in, optional] VARIANT varID);
 
-    [hidden, propput, id(DISPID_ACC_NAME)] HRESULT accName([in]VARIANT varID, [in]BSTR pszName);
-    [hidden, propput, id(DISPID_ACC_VALUE)] HRESULT accValue([in]VARIANT varID, [out, retval]BSTR pszValue);
+    [hidden, propput, id(DISPID_ACC_NAME)] HRESULT accName([in, optional] VARIANT varID, [in] BSTR name);
+    [hidden, propput, id(DISPID_ACC_VALUE)] HRESULT accValue([in, optional] VARIANT varID, [in] BSTR value);
 }
 
 [