diff --git a/controllers/admin/AdminCustomersController.php b/controllers/admin/AdminCustomersController.php
index 17823f6e5..888726033 100644
--- a/controllers/admin/AdminCustomersController.php
+++ b/controllers/admin/AdminCustomersController.php
@@ -28,7 +28,7 @@
 class AdminCustomersControllerCore extends AdminController
 {
 	protected $delete_mode;
-	
+
 	protected $_defaultOrderBy = 'date_add';
 	protected $_defaultOrderWay = 'DESC';
 
@@ -50,8 +50,8 @@ class AdminCustomersControllerCore extends AdminController
 
 		$this->default_form_language = $this->context->language->id;
 
-		$genders_icon = array('default' => 'unknown.gif');
-		$genders = array(0 => $this->l('?'));
+		$genders_icon = array();
+		$genders = array();
 		foreach (Gender::getGenders() as $gender)
 		{
 			$gender_file = 'genders/'.$gender->id.'.jpg';
@@ -380,7 +380,7 @@ class AdminCustomersControllerCore extends AdminController
 					unset($groups[$key]);
 		}
 
-		$this->fields_form['input'] = array_merge($this->fields_form['input'], 
+		$this->fields_form['input'] = array_merge($this->fields_form['input'],
 				array(
 					array(
 								'type' => 'group',
@@ -873,11 +873,11 @@ class AdminCustomersControllerCore extends AdminController
 
 		return $tpl->fetch();
 	}
-	
+
 	/**
-	 * add to $this->content the result of Customer::SearchByName 
+	 * add to $this->content the result of Customer::SearchByName
 	 * (encoded in json)
-	 * 
+	 *
 	 * @return void
 	 */
 	public function ajaxProcessSearchCustomers()
diff --git a/install-dev/data/img/genders/Unknown.jpg b/install-dev/data/img/genders/Unknown.jpg
new file mode 100644
index 000000000..8e4544ca8
Binary files /dev/null and b/install-dev/data/img/genders/Unknown.jpg differ
diff --git a/install-dev/data/xml/gender.xml b/install-dev/data/xml/gender.xml
index fd324a60d..242928b43 100644
--- a/install-dev/data/xml/gender.xml
+++ b/install-dev/data/xml/gender.xml
@@ -7,5 +7,6 @@
     <gender id="Mr" type="0"/>
     <gender id="Ms" type="1"/>
     <gender id="Miss" type="1"/>
+    <gender id="Unknown" type="2"/>
   </entities>
 </entity_gender>
diff --git a/install-dev/fixtures/apple/data/customer.xml b/install-dev/fixtures/apple/data/customer.xml
index e99c5f93f..c194b8732 100644
--- a/install-dev/fixtures/apple/data/customer.xml
+++ b/install-dev/fixtures/apple/data/customer.xml
@@ -19,7 +19,7 @@
     <field name="is_guest"/>
   </fields>
   <entities>
-    <customer id="John" id_gender="" id_default_group="3" firstname="John" lastname="DOE" passwd="75b019568bc6c84dda367661e855bdc2" last_passwd_gen="2012-02-01 09:08:06" birthday="1970-01-15" newsletter="1" ip_registration_newsletter="" newsletter_date_add="0000-00-00 00:00:00" optin="1" secure_key="b59e02456693eb0903a3645512ac9e1a" active="1" is_guest="0">
+    <customer id="John" id_gender="4" id_default_group="3" firstname="John" lastname="DOE" passwd="75b019568bc6c84dda367661e855bdc2" last_passwd_gen="2012-02-01 09:08:06" birthday="1970-01-15" newsletter="1" ip_registration_newsletter="" newsletter_date_add="0000-00-00 00:00:00" optin="1" secure_key="b59e02456693eb0903a3645512ac9e1a" active="1" is_guest="0">
       <email>pub@prestashop.com</email>
       <note/>
     </customer>
diff --git a/install-dev/langs/de/data/gender.xml b/install-dev/langs/de/data/gender.xml
index 9f9c63786..23195ef22 100644
--- a/install-dev/langs/de/data/gender.xml
+++ b/install-dev/langs/de/data/gender.xml
@@ -3,4 +3,5 @@
   <gender id="Mr" name="Herr"/>
   <gender id="Ms" name="Frau"/>
   <gender id="Miss" name="Miss"/>
+  <gender id="Unknown" name="Unbekannte"/>
 </entity_gender>
diff --git a/install-dev/langs/en/data/gender.xml b/install-dev/langs/en/data/gender.xml
index 023a5e78d..74a7e4e79 100644
--- a/install-dev/langs/en/data/gender.xml
+++ b/install-dev/langs/en/data/gender.xml
@@ -3,4 +3,5 @@
   <gender id="Mr" name="Mr."/>
   <gender id="Ms" name="Ms."/>
   <gender id="Miss" name="Miss"/>
+  <gender id="Unknown" name="Unknown"/>
 </entity_gender>
diff --git a/install-dev/langs/es/data/gender.xml b/install-dev/langs/es/data/gender.xml
index 506554ad3..9d5398fe2 100644
--- a/install-dev/langs/es/data/gender.xml
+++ b/install-dev/langs/es/data/gender.xml
@@ -3,4 +3,5 @@
   <gender id="Mr" name="Sr."/>
   <gender id="Ms" name="Sra."/>
   <gender id="Miss" name="Miss"/>
+  <gender id="Unknown" name="Desconocido"/>
 </entity_gender>
diff --git a/install-dev/langs/fr/data/gender.xml b/install-dev/langs/fr/data/gender.xml
index 2a62da434..2e106b983 100644
--- a/install-dev/langs/fr/data/gender.xml
+++ b/install-dev/langs/fr/data/gender.xml
@@ -3,4 +3,5 @@
   <gender id="Mr" name="M."/>
   <gender id="Ms" name="Mme"/>
   <gender id="Miss" name="Melle"/>
+  <gender id="Unknown" name="Inconnu"/>
 </entity_gender>
diff --git a/install-dev/langs/it/data/gender.xml b/install-dev/langs/it/data/gender.xml
index cd5188609..268aff4df 100644
--- a/install-dev/langs/it/data/gender.xml
+++ b/install-dev/langs/it/data/gender.xml
@@ -3,4 +3,5 @@
   <gender id="Mr" name="Sig."/>
   <gender id="Ms" name="Sig.ra"/>
   <gender id="Miss" name="Miss"/>
+  <gender id="Unknown" name="Sconosciuto"/>
 </entity_gender>
diff --git a/install-dev/upgrade/php/add_unknown_gender.php b/install-dev/upgrade/php/add_unknown_gender.php
new file mode 100644
index 000000000..a002ee747
--- /dev/null
+++ b/install-dev/upgrade/php/add_unknown_gender.php
@@ -0,0 +1,63 @@
+<?php
+/*
+* 2007-2011 PrestaShop
+*
+* NOTICE OF LICENSE
+*
+* This source file is subject to the Open Software License (OSL 3.0)
+* that is bundled with this package in the file LICENSE.txt.
+* It is also available through the world-wide-web at this URL:
+* http://opensource.org/licenses/osl-3.0.php
+* If you did not receive a copy of the license and are unable to
+* obtain it through the world-wide-web, please send an email
+* to license@prestashop.com so we can send you a copy immediately.
+*
+* DISCLAIMER
+*
+* Do not edit or add to this file if you wish to upgrade PrestaShop to newer
+* versions in the future. If you wish to customize PrestaShop for your
+* needs please refer to http://www.prestashop.com for more information.
+*
+*  @author PrestaShop SA <contact@prestashop.com>
+*  @copyright  2007-2011 PrestaShop SA
+*  @version  Release: $Revision$
+*  @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
+*  International Registered Trademark & Property of PrestaShop SA
+*/
+
+function add_unknown_gender()
+{
+	$res = true;
+
+	// creates the new gender
+	$id_type = 2;
+	$res &= Db::getInstance()->execute('
+		INSERT INTO `'._DB_PREFIX_.'gender` (`type`)
+		VALUES ('.(int)$id_type.')');
+
+	// retrieves its id
+	$id_gender = Db::getInstance()->Insert_ID();
+
+	// inserts lang values
+	$languages = Db::getInstance()->executeS('SELECT * FROM `'._DB_PREFIX_.'lang`');
+	$lang_names = array(
+		1 => 'Unknown',
+		2 => 'Unbekannte',
+		3 => 'Desconocido',
+		4 => 'Inconnu',
+		5 => 'Sconosciuto',
+	);
+
+	foreach ($languages as $lang)
+	{
+		$res &= Db::getInstance()->execute('
+			INSERT INTO `'._DB_PREFIX_.'gender_lang` (`id_gender`, `id_lang`, `name`) VALUES
+				('.(int)$id_gender.', '.(int)$lang['id_lang'].', \''.pSQL($lang_names[$lang['id_lang']]).'\')');
+	}
+
+	// for all clients where id gender is 0, sets the new id gender
+	$res &= Db::getInstance()->execute('
+		UPDATE `'._DB_PREFIX_.'customers`
+		SET `id_gender` = '.(int)$id_gender.'
+		WHERE `id_gender` = 0');
+}
diff --git a/install-dev/upgrade/sql/1.5.0.6.sql b/install-dev/upgrade/sql/1.5.0.6.sql
index 8a019a79b..0cb9a4ce9 100644
--- a/install-dev/upgrade/sql/1.5.0.6.sql
+++ b/install-dev/upgrade/sql/1.5.0.6.sql
@@ -9,6 +9,8 @@ SET o.`current_state` = (
 	LIMIT 1
 );
 
+/* PHP:add_unknown_gender(); */;
+
 ALTER TABLE `PREFIX_cart_rule` ADD `gift_product_attribute` int(10) unsigned NOT NULL default 0 AFTER `gift_product`;
 
 UPDATE `PREFIX_product` set is_virtual = 1 WHERE id_product IN (SELECT id_product FROM `PREFIX_product_download` WHERE active = 1);