#[warning="-notation-incompatible-prefix"]
    Local Notation "R *" := (clos_refl_trans R)
      (at level 8, no associativity, format "R *").

Lemma clos_rst1n_sym : forall x y, clos_refl_sym_trans_1n R x y -> clos_refl_sym_trans_1n R y x.