diff --git a/include/objbase.h b/include/objbase.h
index 5f58bb0d5e0..d468e8a5317 100644
--- a/include/objbase.h
+++ b/include/objbase.h
@@ -453,6 +453,7 @@ HRESULT WINAPI MonikerRelativePathTo(LPMONIKER pmkSrc, LPMONIKER pmkDest, LPMONI
 #define STGM_FAILIFTHERE	0x00000000
 #define STGM_NOSCRATCH		0x00100000
 #define STGM_NOSNAPSHOT		0x00200000
+#define STGM_DIRECT_SWMR	0x00400000
 
 typedef struct tagSTGOPTIONS
 {