diff --git a/ipv6ula/migrations/0003_auto_20201204_2201.py b/ipv6ula/migrations/0003_auto_20201204_2201.py
new file mode 100644
index 0000000..239e74b
--- /dev/null
+++ b/ipv6ula/migrations/0003_auto_20201204_2201.py
@@ -0,0 +1,19 @@
+# Generated by Django 3.1.4 on 2020-12-04 22:01
+
+from django.db import migrations, models
+import ipv6ula.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('ipv6ula', '0002_auto_20201204_2019'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='ula',
+            name='prefix',
+            field=models.GenericIPAddressField(protocol='IPv6', unique=True, validators=[ipv6ula.models.validate_ula_prefix]),
+        ),
+    ]
diff --git a/ipv6ula/models.py b/ipv6ula/models.py
index bda2f46..b408796 100644
--- a/ipv6ula/models.py
+++ b/ipv6ula/models.py
@@ -2,8 +2,22 @@ from django.contrib.auth.models import AbstractUser
 from django.contrib.auth import get_user_model
 from django.db import models
 from django.core.exceptions import ValidationError
+from django.utils.translation import gettext_lazy as _
 
 
+import ipaddress
+
+def validate_ula_prefix(prefix):
+    ula_net = ipaddress.IPv6Network("fd00::/8")
+    net_str = f"{prefix}/48"
+    net = ipaddress.IPv6Network(net_str, strict=False)
+
+    if not net.subnet_of(ula_net):
+        raise ValidationError(
+            _(f"Prefix {prefix} is not within ULA range ({ula_net})"),
+            code='invalid',
+            params = {'prefix': prefix }
+        )
 
 
 class User(AbstractUser):
@@ -15,17 +29,21 @@ class ULA(models.Model):
         on_delete=models.CASCADE
     )
 
-    prefix = models.GenericIPAddressField(protocol='IPv6', unique=True)
+    prefix = models.GenericIPAddressField(protocol='IPv6', unique=True, validators=[validate_ula_prefix])
     name = models.CharField(max_length=256)
     organization = models.CharField(max_length=256)
     website = models.URLField()
 
-    # def save(self, *args, **kwargs):
-    #     """
-    #     Ensure we only save the first IPv6 address of the network
-    #     """
+    def save(self, *args, **kwargs):
+        """
+        Ensure we only save the first IPv6 address of the network
+        """
 
-    #     super().save(*args, **kwargs)
+        net_str = f"{self.prefix}/48"
+        net = ipaddress.IPv6Network(net_str, strict=False)
+        self.prefix = str(net[0])
+
+        super().save(*args, **kwargs)
 
     def __str__(self):
         return f"{self.prefix}"
diff --git a/ipv6ula/templates/ipv6ula/ula_form.html b/ipv6ula/templates/ipv6ula/ula_form.html
index 8eeae74..20d6abd 100644
--- a/ipv6ula/templates/ipv6ula/ula_form.html
+++ b/ipv6ula/templates/ipv6ula/ula_form.html
@@ -6,11 +6,17 @@
   <div class="row">
     <div class="col">
 
-    All ULA prefixes are /48 networks. Simply add the first IP address
-    (without any netmask, for instance fd23:2323:2323::).
+      <p>
+        All ULA prefixes are /48 networks. Simply add the first IP address
+        (without any netmask, for instance fd23:2323:2323::).
+
+        You can choose the name of your liking and an optional
+        organization name.
+      </p>
+      <p>
+        ULA prefixes must be part of the fd00::/8 network.
+      </p>
 
-    You can choose the name of your liking and an optional
-    organization name.
     </div>
 
     <div class="col">
diff --git a/ipv6ula/views.py b/ipv6ula/views.py
index ccb5696..70ae514 100644
--- a/ipv6ula/views.py
+++ b/ipv6ula/views.py
@@ -25,21 +25,6 @@ class SubmitView(LoginRequiredMixin, CreateView):
 
     def form_valid(self, form):
         form.instance.owner = self.request.user
-
-        prefix = form.cleaned_data['prefix']
-
-        ula_net = ipaddress.IPv6Network("fd00::/8")
-        net_str = f"{prefix}/48"
-        net = ipaddress.IPv6Network(net_str, strict=False)
-
-        if not net.subnet_of(ula_net):
-            raise ValidationError(f"Prefix {prefix} is not within ULA range ({ula_net})",
-                                  code='invalid',
-                                  params = {'prefix': 42 }
-                                  )
-
-        self.prefix = str(net[0])
-
         return super(SubmitView, self).form_valid(form)
 
 class LoginView(auth_views.LoginView):