diff --git a/hw/9pfs/virtio-9p.h b/hw/9pfs/virtio-9p.h
index 6273b85..7f88356 100644
--- a/hw/9pfs/virtio-9p.h
+++ b/hw/9pfs/virtio-9p.h
@@ -212,6 +212,12 @@
     int fd;
     DIR *dir;
     V9fsXattr xattr;
+    /*
+     * private pointer for fs drivers, that
+     * have its own internal representation of
+     * open files.
+     */
+    void *private;
 };
 
 struct V9fsFidState