diff --git a/ejemplos/frontend/flask-example/app/templates/signup.html b/ejemplos/frontend/flask-example/app/templates/signup.html
index df43805..01e0f49 100644
--- a/ejemplos/frontend/flask-example/app/templates/signup.html
+++ b/ejemplos/frontend/flask-example/app/templates/signup.html
@@ -13,6 +13,7 @@ <h3 class="title">Sign Up</h3>
         {% endwith %}
 
         <form method="POST" action="/signup">
+            {{ form.hidden_tag() }}
             <div class="field">
                 <div class="control">
                     <input class="input is-large" type="email" name="email" placeholder="Email" autofocus="">
@@ -35,4 +36,4 @@ <h3 class="title">Sign Up</h3>
         </form>
     </div>
 </div>
-{% endblock %}
\ No newline at end of file
+{% endblock %}