1 files changed, 3 insertions, 0 deletions
diff --git a/src/class.c b/src/class.c
index ac0bb8ede..d037a8abb 100644
--- a/src/class.c
+++ b/src/class.c
@@ -470,6 +470,9 @@ mrb_define_method_id(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_func_t f
   int ai = mrb_gc_arena_save(mrb);
 
   MRB_METHOD_FROM_FUNC(m, func);
+  if (aspec == MRB_ARGS_NONE()) {
+    MRB_METHOD_NOARG_SET(m);
+  }
   mrb_define_method_raw(mrb, c, mid, m);
   mrb_gc_arena_restore(mrb, ai);
 }