diff --git a/app/models/Data/Base.php b/app/models/Data/Base.php
index 2223d4b..59a92be 100644
--- a/app/models/Data/Base.php
+++ b/app/models/Data/Base.php
@@ -6,4 +6,21 @@ use Phalcon\Mvc\Model;
 
 class Base extends Model
 {
+    /**
+     * {@inheritdoc}
+     *
+     * Phalcon throws an exception if no valid snapshot data is present.
+     *
+     * We override this behaviour by treating no
+     * snapshot data (new row) as changed.
+     *
+     * @param string|array $fieldName
+     * @param boolean $allFields
+     * @return bool
+     */
+    public function hasChanged($fieldName = null, $allFields = false)
+    {
+        return $this->hasSnapshotData() === false
+            || parent::hasChanged($fieldName, $allFields);
+    }
 }
diff --git a/app/models/Data/User.php b/app/models/Data/User.php
index d813e8b..335a874 100644
--- a/app/models/Data/User.php
+++ b/app/models/Data/User.php
@@ -2,13 +2,12 @@
 
 namespace App\Model\Data;
 
-use Phalcon\Mvc\Model,
-    Phalcon\Validation,
+use Phalcon\Validation,
     Phalcon\Validation\Validator\Callback as CallbackValidator,
     InvalidArgumentException,
     Httpcb\OAuth\UserData\UserDataInterface;
 
-class User extends Model
+class User extends Base
 {
     const STATUS_ACTIVE         = 'Active';
     const STATUS_DELETED        = 'Deleted';
@@ -49,19 +48,31 @@ class User extends Model
 
     public function validation()
     {
-        // Validation
-        $validator = new Validation();
+        $rules = [
+            'username' => new CallbackValidator([
+                'callback' => function () {
+                    return $this->findFirstByUsername($this->getUsername()) === false;
+                },
+                'message' => 'The username already exists.'
+            ]),
+            'email' => new CallbackValidator([
+                'callback' => function() {
+                    return $this->findFirstByEmail($this->getEmail()) === false;
+                },
+                'message' => 'The email address already exists.'
+            ])
+        ];
 
-        $validator->add('username', new CallbackValidator([
-            'callback' => function() { return $this->findFirstByUsername($this->getUsername()) === false; },
-            'message' => 'The username already exists.'
-        ]));
-        $validator->add('email', new CallbackValidator([
-            'callback' => function() { return $this->findFirstByEmail($this->getEmail()) === false; },
-            'message' => 'The email address already exists.'
-        ]));
+        $validation = new Validation();
+        foreach($rules as $field => $validator) {
 
-        return $this->validate($validator);
+            // Only validate changed fields.
+            if ($this->hasChanged($field)) {
+                $validation->add($field, $validator);
+            }
+        }
+
+        return $this->validate($validation);
     }
 
     /**