diff --git a/demos/calc-two/_tags b/demos/calc-two/_tags
index 7c7482ee22d42435c0e831959b65b5407dc1c977..e76793bd5ea4c5fd8fb61a2436b04e85e1324de6 100644
--- a/demos/calc-two/_tags
+++ b/demos/calc-two/_tags
@@ -1,3 +1,5 @@
 <tokens.mlypack>: only_tokens
 <algebraic.mlypack>: external_tokens(Tokens)
 <reverse.mlypack>: external_tokens(Tokens)
+<reverse.mly>: unused_token(LPAREN)
+<reverse.mly>: unused_token(RPAREN)
diff --git a/demos/calc-two/myocamlbuild.ml b/demos/calc-two/myocamlbuild.ml
index 8bdc26f5e8a2b014fb942ab31ab2bd2d3b4638da..0520a4895fa1ceea90331f8dc3c29e270fb242a4 100644
--- a/demos/calc-two/myocamlbuild.ml
+++ b/demos/calc-two/myocamlbuild.ml
@@ -1,25 +1,31 @@
 open Ocamlbuild_plugin
 open Command
 
+
+(* Define ocamlbuild flags [only_tokens] and [external_tokens(Foo)] and
+   [unused_token(Bar)] which correspond to menhir's [--only-tokens] and
+   [--external-tokens Foo] and [--unused-token Bar]. When they are used, these
+   flags should be passed both to [menhir] and to [menhir --raw-depend]. *)
+
 let menhir_flags() =
-  (* Define two ocamlbuild flags [only_tokens] and [external_tokens(Foo)]
-     which correspond to menhir's [--only-tokens] and [--external-tokens Foo].
-     When they are used, these flags should be passed both to [menhir] and to
-     [menhir --raw-depend]. *)
   List.iter (fun mode ->
     
     flag [ mode; "only_tokens" ] (S[A "--only-tokens"]);
 
     pflag [ mode ] "external_tokens" (fun name ->
       S[A "--external-tokens"; A name]
+    );
+
+    pflag [ mode ] "unused_token" (fun name ->
+      S[A "--unused-token"; A name]
     )
-  
+      
   ) [ "menhir"; "menhir_ocamldep" ]
 
 let () =
   dispatch (fun event ->
     match event with
     | After_rules ->
-        menhir_flags()
+      menhir_flags()
     | _ -> ()
   )