diff --git a/lib/Net/LDAP3.php b/lib/Net/LDAP3.php
index 48bb5c705dbce660d5055899d2560c2d7c63dc02..7df93ad044d245e7bc423e3e158a00eb818af081 100644
--- a/lib/Net/LDAP3.php
+++ b/lib/Net/LDAP3.php
@@ -42,6 +42,9 @@ require_once __DIR__ . '/LDAP3/Result.php';
 class Net_LDAP3
 {
     const CONTROL_EFFECTIVE_RIGHTS = '1.3.6.1.4.1.42.2.27.9.5.2';
+    const CONTROL_SORT_REQUEST     = '1.2.840.113556.1.4.473';
+    const CONTROL_VLV_REQUEST      = '2.16.840.1.113730.3.4.9';
+
 
     public $conn;
     public $vlv_active = false;
@@ -2865,7 +2868,7 @@ class Net_LDAP3
     private function _vlv_set_controls($sort, $list_page, $page_size, $search = null)
     {
         $sort_ctrl = array(
-            'oid'   => "1.2.840.113556.1.4.473",
+            'oid'   => self::CONTROL_SORT_REQUEST,
             'value' => self::_sort_ber_encode($sort)
         );
 
@@ -2874,7 +2877,7 @@ class Net_LDAP3
         }
 
         $vlv_ctrl  = array(
-            'oid' => "2.16.840.1.113730.3.4.9",
+            'oid' => self::CONTROL_VLV_REQUEST,
             'value' => self::_vlv_ber_encode(
                     $offset = ($list_page-1) * $page_size + 1,
                     $page_size,