diff --git a/include/vfw.h b/include/vfw.h
index 4ab0db6..f70499a 100644
--- a/include/vfw.h
+++ b/include/vfw.h
@@ -985,6 +985,7 @@
 DEFINE_AVIGUID(IID_IGetFrame,           0x00020023, 0, 0);
 DEFINE_AVIGUID(IID_IAVIEditStream,      0x00020024, 0, 0);
 
+DEFINE_AVIGUID(CLSID_AVISimpleUnMarshal,0x00020009, 0, 0);
 DEFINE_AVIGUID(CLSID_AVIFile,           0x00020000, 0, 0);
 
 /*****************************************************************************