diff --git a/serveradmin/serverdb/migrations/0016_optional_servertype_for_relation.py b/serveradmin/serverdb/migrations/0016_optional_servertype_for_relation.py
new file mode 100644
index 00000000..49945bfc
--- /dev/null
+++ b/serveradmin/serverdb/migrations/0016_optional_servertype_for_relation.py
@@ -0,0 +1,21 @@
+# Generated by Django 3.2.23 on 2023-11-03 08:04
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('serverdb', '0015_attribute_history_field'),
+    ]
+
+    operations = [
+        migrations.RunSQL(
+            "ALTER TABLE attribute DROP CONSTRAINT IF EXISTS attribute_target_servertype_id_check"
+        ),
+        # This is the same as before but without a check for type relation.
+        migrations.RunSQL(
+            "ALTER TABLE attribute ADD CONSTRAINT attribute_target_servertype_id_check "
+            "CHECK((type IN ('domain', 'supernet', 'relation')) = (target_servertype_id IS NOT NULL OR type = 'relation'))"
+        ),
+    ]
diff --git a/serveradmin/serverdb/models.py b/serveradmin/serverdb/models.py
index 06fad557..7a625521 100644
--- a/serveradmin/serverdb/models.py
+++ b/serveradmin/serverdb/models.py
@@ -591,8 +591,6 @@ class Meta:
         index_together = [['attribute', 'value']]
 
     def save_value(self, value):
-        target_servertype = self.attribute.target_servertype
-
         try:
             target_server = Server.objects.get(hostname=value)
         except Server.DoesNotExist:
@@ -600,7 +598,8 @@ def save_value(self, value):
                 'No server with hostname "{0}" exist.'.format(value)
             )
 
-        if target_server.servertype != target_servertype:
+        target_servertype = self.attribute.target_servertype
+        if target_servertype and target_server.servertype != target_servertype:
             raise ValidationError(
                 'Attribute "{0}" has to be from servertype "{1}".'
                 .format(self.attribute, self.attribute.target_servertype)