embed sentinel
diff --git a/src/core/ngx_open_file_cache.h b/src/core/ngx_open_file_cache.h
index cc0d899..272bcb5 100644
--- a/src/core/ngx_open_file_cache.h
+++ b/src/core/ngx_open_file_cache.h
@@ -63,6 +63,7 @@
 
 typedef struct {
     ngx_rbtree_t             rbtree;
+    ngx_rbtree_node_t        sentinel;
     ngx_cached_open_file_t   list_head;
     ngx_cached_open_file_t   list_tail;