diff --git a/sdk/include/xdk/winnt_old.h b/sdk/include/xdk/winnt_old.h
index 75e86392711..ab28be40902 100644
--- a/sdk/include/xdk/winnt_old.h
+++ b/sdk/include/xdk/winnt_old.h
@@ -212,6 +212,7 @@
 #define FILE_ATTRIBUTE_NOT_CONTENT_INDEXED    0x00002000
 #define FILE_ATTRIBUTE_ENCRYPTED        0x00004000
 #define FILE_ATTRIBUTE_INTEGRITY_STREAM   0x00008000
+#define FILE_ATTRIBUTE_VIRTUAL 0x00010000
 #define FILE_ATTRIBUTE_VALID_FLAGS        0x00007fb7
 #define FILE_ATTRIBUTE_VALID_SET_FLAGS        0x000031a7