diff -r ec62453fc8a6 -r 1ecf4dbbc60c src/tree.c
--- a/src/tree.c	Fri Dec 20 21:25:33 2024 +0100
+++ b/src/tree.c	Sat Dec 21 21:03:28 2024 +0100
@@ -403,7 +403,7 @@
     return iter->node;
 }
 
-__attribute__((__nonnull__))
+cx_attr_nonnull
 static void cx_tree_visitor_enqueue_siblings(
         struct cx_tree_visitor_s *iter, void *node, ptrdiff_t loc_next) {
     node = tree_next(node);