diff --git a/src/class.c b/src/class.c
index cf03a0197..65d8cd3fb 100644
--- a/src/class.c
+++ b/src/class.c
@@ -3191,6 +3191,7 @@ mrb_init_class(mrb_state *mrb)
   mrb_define_private_method_id(mrb, mod, MRB_SYM(method_added),            mrb_do_nothing,           MRB_ARGS_REQ(1));
   mrb_define_private_method_id(mrb, mod, MRB_SYM(method_removed),          mrb_do_nothing,           MRB_ARGS_REQ(1));
   mrb_define_private_method_id(mrb, mod, MRB_SYM(method_undefined),        mrb_do_nothing,           MRB_ARGS_REQ(1));
+  mrb_define_private_method_id(mrb, mod, MRB_SYM(const_added),             mrb_do_nothing,           MRB_ARGS_REQ(1));
 
   mrb_undef_method_id(mrb, cls, MRB_SYM(append_features));
   mrb_undef_method_id(mrb, cls, MRB_SYM(prepend_features));