diff --git a/externals/mrpeach/op~/op~.c b/externals/mrpeach/op~/op~.c
index 8a15bc3a35760ddfa9d85678056583717ec8aad9..ec3062524a1a1d31bd0c288b01af7d8b46c27b48 100644
--- a/externals/mrpeach/op~/op~.c
+++ b/externals/mrpeach/op~/op~.c
@@ -228,7 +228,7 @@ void op_tilde_setup(void)
 {
     op_tilde_class = class_new(gensym("op~"), (t_newmethod)op_tilde_new, 0,
         sizeof(t_op_tilde), 0, A_GIMME, 0);
-    class_addmethod(op_tilde_class, (t_method)op_tilde_dsp, gensym("dsp"), 0);
+    class_addmethod(op_tilde_class, (t_method)op_tilde_dsp, gensym("dsp"), A_CANT, 0);
     class_addmethod(op_tilde_class, (t_method)op_tilde_help, gensym("help"), 0);
     class_addmethod(op_tilde_class, (t_method)op_tilde_op, gensym("op"), A_DEFSYMBOL, 0);
     CLASS_MAINSIGNALIN(op_tilde_class, t_op_tilde, x_f);