diff --git a/server.py b/server.py
index bbf9207..c7f1770 100644
--- a/server.py
+++ b/server.py
@@ -96,8 +96,8 @@ class Dispositivo(db.Model):
     tipo = db.Column(db.String)
     marca = db.Column(db.String)
     modello = db.Column(db.String)
-    inv_ced = db.Column(db.Integer)
-    inv_ente = db.Column(db.Integer)
+    inv_ced = db.Column(db.Integer, unique=True)
+    inv_ente = db.Column(db.Integer, unique=True)
     fornitore = db.Column(db.String)
     seriale = db.Column(db.String)
     ip = db.Column(db.String)
@@ -550,23 +550,25 @@ def page_disp_show(did):
         return render_template("dispositivo/show.htm", dispositivo=disp, accessi=accessi, impiegati=impiegati,
                                pagetype="disp", user=session.get("username"), opzioni=opzioni, reti=reti)
     else:
-        if request.form["inv_ced"]:
-            try:
-                int(request.form["inv_ced"])
-            except ValueError:
-                return render_template("error.htm", error="Il campo Inventario CED deve contenere un numero.")
-        if request.form["inv_ente"]:
-            try:
-                int(request.form["inv_ente"])
-            except ValueError:
-                return render_template("error.htm", error="Il campo Inventario ente deve contenere un numero.")
         disp = Dispositivo.query.get_or_404(did)
         accessi = Accesso.query.filter_by(did=did).all()
+        if request.form["inv_ced"]:
+            try:
+                disp.inv_ced = int(request.form["inv_ced"])
+            except ValueError:
+                return render_template("error.htm", error="Il campo Inventario CED deve contenere un numero.")
+        else:
+            disp.inv_ced = None
+        if request.form["inv_ente"]:
+            try:
+                disp.inv_ente = int(request.form["inv_ente"])
+            except ValueError:
+                return render_template("error.htm", error="Il campo Inventario ente deve contenere un numero.")
+        else:
+            disp.inv_ente = None
         disp.tipo = request.form['tipo']
         disp.marca = request.form['marca']
         disp.modello = request.form['modello']
-        disp.inv_ced = int(request.form['inv_ced']) if request.form["inv_ced"] else None
-        disp.inv_ente = int(request.form['inv_ente']) if request.form["inv_ced"] else None
         disp.fornitore = request.form['fornitore']
         disp.nid = int(request.form['rete'])
         disp.ip = request.form['ip']
diff --git a/templates/dispositivo/list.htm b/templates/dispositivo/list.htm
index 8353342..e473d90 100644
--- a/templates/dispositivo/list.htm
+++ b/templates/dispositivo/list.htm
@@ -22,7 +22,7 @@
             <tr>
                 <td>{{ d[0].dispositivo.tipo }}</td>
                 <td>{% for u in d %}<p>{{ u.impiegato.nomeimpiegato }}</p>{% endfor %}</td>
-                <td>{{ d[0].dispositivo.inv_ced }}</td>
+                <td>{% if d[0].dispositivo.inv_ced %}{{ d[0].dispositivo.inv_ced }}{% endif %}</td>
                 <td>{{ d[0].dispositivo.marca }}</td>
                 <td>{{ d[0].dispositivo.modello }}</td>
                 <td>{{ d[0].dispositivo.fornitore }}</td>
diff --git a/templates/dispositivo/show.htm b/templates/dispositivo/show.htm
index 315ddcc..b52d702 100644
--- a/templates/dispositivo/show.htm
+++ b/templates/dispositivo/show.htm
@@ -73,13 +73,13 @@
         <div class="form-group">
             <label class="col-xs-2" for="form-ced">Inventario CED</label>
             <div class="col-xs-10">
-                <input id="form-ced" class="form-control" type="text" placeholder="Inventario CED" name="inv_ced" value="{{ dispositivo.inv_ced }}">
+                <input id="form-ced" class="form-control" type="text" placeholder="Inventario CED" name="inv_ced" {% if dispositivo.inv_ced %}value="{{ dispositivo.inv_ced }}"{% endif %}>
             </div>
         </div>
         <div class="form-group">
             <label class="col-xs-2" for="form-ente">Inventario ente</label>
             <div class="col-xs-10">
-                <input id="form-ente" class="form-control" type="text" placeholder="Inventario ente" name="inv_ente" value="{{ dispositivo.inv_ente }}">
+                <input id="form-ente" class="form-control" type="text" placeholder="Inventario ente" name="inv_ente" {% if dispositivo.inv_ente %}value="{{ dispositivo.inv_ente }}"{% endif %}>
             </div>
         </div>
         <div class="form-group">