diff --git a/reactos/include/psdk/mlang.idl b/reactos/include/psdk/mlang.idl
index b29d87273dd..6ce148648c5 100644
--- a/reactos/include/psdk/mlang.idl
+++ b/reactos/include/psdk/mlang.idl
@@ -36,7 +36,7 @@ interface IMLangCodePages : IUnknown
 {
     HRESULT GetCharCodePages(      
         [in] WCHAR chSrc,
-        DWORD *pdwCodePages);
+        [out] DWORD *pdwCodePages);
     HRESULT GetStrCodePages(      
         [in, size_is(cchSrc)] const WCHAR *pszSrc,
         [in] long cchSrc,