diff --git a/src/proc.c b/src/proc.c
index 1b573c3ac..f8139a8a7 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -271,7 +271,6 @@ mrb_proc_init_copy(mrb_state *mrb, mrb_value self)
   return self;
 }
 
-/* 15.2.17.4.2 */
 static mrb_value
 proc_arity(mrb_state *mrb, mrb_value self)
 {
@@ -464,11 +463,11 @@ mrb_init_proc(mrb_state *mrb)
 
   mrb_define_class_method(mrb, mrb->proc_class, "new", mrb_proc_s_new, MRB_ARGS_NONE()|MRB_ARGS_BLOCK());
   mrb_define_method(mrb, mrb->proc_class, "initialize_copy", mrb_proc_init_copy, MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, mrb->proc_class, "arity", proc_arity, MRB_ARGS_NONE());
+  mrb_define_method(mrb, mrb->proc_class, "arity", proc_arity, MRB_ARGS_NONE()); /* 15.2.17.4.2 */
 
   MRB_METHOD_FROM_PROC(m, &call_proc);
-  mrb_define_method_raw(mrb, mrb->proc_class, MRB_SYM(call), m);
-  mrb_define_method_raw(mrb, mrb->proc_class, MRB_OPSYM(aref), m);
+  mrb_define_method_raw(mrb, mrb->proc_class, MRB_SYM(call), m);   /* 15.2.17.4.3 */
+  mrb_define_method_raw(mrb, mrb->proc_class, MRB_OPSYM(aref), m); /* 15.2.17.4.1 */
 
   mrb_define_method(mrb, mrb->kernel_module,       "lambda", proc_lambda, MRB_ARGS_NONE()|MRB_ARGS_BLOCK()); /* 15.3.1.3.27 */
 }