diff --git a/util/dukweb_base.yaml b/util/dukweb_base.yaml
index a88065a8..87766a65 100644
--- a/util/dukweb_base.yaml
+++ b/util/dukweb_base.yaml
@@ -2,3 +2,5 @@ DUK_USE_SELF_TESTS: true
 #DUK_USE_ASSERTIONS: true
 DUK_USE_FATAL_HANDLER:
   verbatim: "#define DUK_USE_FATAL_HANDLER(udata,msg) do {dukweb_fatal_handler((udata),(msg));abort();} while (0)"
+
+DUK_USE_SYMBOL_BUILTIN: true