diff --git a/include/mfreadwrite.idl b/include/mfreadwrite.idl
index 5cb3501be53..834aa093bdf 100644
--- a/include/mfreadwrite.idl
+++ b/include/mfreadwrite.idl
@@ -15,10 +15,9 @@
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
-import "unknwn.idl";
-import "objidl.idl";
-import "oaidl.idl";
+
 import "mfobjects.idl";
+import "mftransform.idl";
 
 enum
 {
@@ -121,6 +120,17 @@ interface IMFSinkWriter : IUnknown
     HRESULT GetStatistics([in] DWORD index, [out] MF_SINK_WRITER_STATISTICS *stats);
 };
 
+[
+    object,
+    uuid(588d72ab-5Bc1-496a-8714-b70617141b25),
+    local
+]
+interface IMFSinkWriterEx : IMFSinkWriter
+{
+    HRESULT GetTransformForStream([in] DWORD index, [in] DWORD tindex, [out] GUID *category,
+                                  [out] IMFTransform **transform);
+}
+
 cpp_quote( "HRESULT WINAPI MFCreateSourceReaderFromByteStream(IMFByteStream *stream, IMFAttributes *attributes," )
 cpp_quote( "                                                  IMFSourceReader **reader);" )
 cpp_quote( "HRESULT WINAPI MFCreateSourceReaderFromMediaSource(IMFMediaSource *source, IMFAttributes *attributes," )