diff --git a/MdePkg/Include/Pi/PiDxeCis.h b/MdePkg/Include/Pi/PiDxeCis.h
index 17543fa72b..caed14bd87 100644
--- a/MdePkg/Include/Pi/PiDxeCis.h
+++ b/MdePkg/Include/Pi/PiDxeCis.h
@@ -369,7 +369,8 @@ EFI_STATUS
                                 BaseAddress and Length cannot be modified.
   @retval EFI_OUT_OF_RESOURCES  There are not enough system resources to modify the attributes of
                                 the memory resource range.
-
+  @retval EFI_NOT_AVAILABLE_YET The attributes cannot be set because CPU architectural protocol is
+                                not available yet.
 **/
 typedef
 EFI_STATUS