diff --git a/lang/ast/iterate.c b/lang/ast/iterate.c
index 1248409..2c95801 100644
--- a/lang/ast/iterate.c
+++ b/lang/ast/iterate.c
@@ -15,6 +15,11 @@ enum ivy_status ivy_ast_node_iterate(
 		struct ivy_ast_node_iterator_entry *it_entry = b_unbox(struct ivy_ast_node_iterator_entry, entry, it_entry);
 		node = b_unbox(struct ivy_ast_node, it_entry, n_it);
 
+		if (!node) {
+			/* this should never happen. */
+			return IVY_ERR_INTERNAL_FAILURE;
+		}
+
 		enum ivy_status status = callback(node, it);
 		if (status != IVY_OK) {
 			return status;