diff --git a/src/core/ngx_rbtree.h b/src/core/ngx_rbtree.h
index de6fef9..af0f2ec 100644
--- a/src/core/ngx_rbtree.h
+++ b/src/core/ngx_rbtree.h
@@ -13,7 +13,7 @@
    ngx_rbtree_t   *left;
    ngx_rbtree_t   *right;
    ngx_rbtree_t   *parent;
-   void           *data;
+   char            color;
 };
 
 extern ngx_rbtree_t  sentinel;