diff --git a/src/Aperophp/Provider/Controller/Member.php b/src/Aperophp/Provider/Controller/Member.php
index a660e7b..cc7dee7 100644
--- a/src/Aperophp/Provider/Controller/Member.php
+++ b/src/Aperophp/Provider/Controller/Member.php
@@ -97,6 +97,11 @@ public function connect(Application $app)
                 if ($form->isValid()) {
                     $data = $form->getData();
 
+                    $username = $data['member']['username'];
+                    if ($app['members']->findOneByUsername($username)) {
+                         $app->abort(500, sprintf("Le nom d'utilisateur '%s' est déjà utilisé.", $username));
+                    }
+
                     $app['db']->beginTransaction();
 
                     try {
diff --git a/src/Aperophp/Repository/Member.php b/src/Aperophp/Repository/Member.php
index e65fbc6..3c21e72 100644
--- a/src/Aperophp/Repository/Member.php
+++ b/src/Aperophp/Repository/Member.php
@@ -23,4 +23,19 @@ public function findOneByUsernameAndPassword($username, $password)
 
         return $this->db->fetchAssoc($sql, array($username, $password));
     }
+
+    /**
+     * findOneByUsername
+     *
+     * @param string $username
+     *
+     * @return array
+     */
+    public function findOneByUsername($username)
+    {
+        $sql = 'SELECT * FROM Member WHERE username = ? AND active = true LIMIT 1';
+
+        return $this->db->fetchAssoc($sql, array($username));
+    }
+
 }