Definition bupd_ret_assert (Q: ret_assert): ret_assert :=
          {| RA_normal := fun rho => bupd (RA_normal Q rho);
             RA_break := fun rho => bupd (RA_break Q rho);
             RA_continue := fun rho => bupd (RA_continue Q rho);
             RA_return := fun v rho => bupd (RA_return Q v rho) |}.

Lemma rguard_bupd: forall {Espec: OracleKind} ge Delta F (P: ret_assert) k, rguard Espec ge Delta (frame_ret_assert P F) k = rguard Espec ge Delta (frame_ret_assert (bupd_ret_assert P) F) k.