diff --git a/tool/mk_builtin_loader.rb b/tool/mk_builtin_loader.rb
index 837f56d696..a100a5318a 100644
--- a/tool/mk_builtin_loader.rb
+++ b/tool/mk_builtin_loader.rb
@@ -36,7 +36,7 @@ def collect_builtin base, iseq_ary, name, bs, inlines
   else
   end
 
-  code = iseq_ary[13]
+  code = iseq_ary[13] + iseq_ary[12]
   params = iseq_ary[10]
   prev_insn = nil
   lineno = nil