diff --git a/include/dmoreg.h b/include/dmoreg.h
index 592cbd30fe2..085234624b4 100644
--- a/include/dmoreg.h
+++ b/include/dmoreg.h
@@ -19,6 +19,8 @@
 #ifndef __DMOREG_H__
 #define __DMOREG_H__
 
+#include "mediaobj.h"
+
 typedef struct _DMO_PARTIAL_MEDIATYPE
 {
    GUID type;