diff --git a/include/ws_functions.inc.php b/include/ws_functions.inc.php
index f125515c6..82635a213 100644
--- a/include/ws_functions.inc.php
+++ b/include/ws_functions.inc.php
@@ -902,6 +902,18 @@ function ws_images_add($params, &$service)
   // fwrite($fh_log, 'input:  '.$params['file_sum']."\n");
   // fwrite($fh_log, 'input:  '.$params['thumbnail_sum']."\n");
 
+  // does the image already exists ?
+  $query = '
+SELECT
+    COUNT(*) AS counter
+  FROM '.IMAGES_TABLE.'
+  WHERE md5sum = \''.$params['file_sum'].'\'
+;';
+  list($counter) = mysql_fetch_row(pwg_query($query));
+  if ($counter != 0) {
+    return new PwgError(500, 'file already exists');
+  }
+
   // current date
   list($dbnow) = mysql_fetch_row(pwg_query('SELECT NOW();'));
   list($year, $month, $day) = preg_split('/[^\d]/', $dbnow, 4);
@@ -986,6 +998,7 @@ function ws_images_add($params, &$service)
     'filesize' => floor(filesize($file_path)/1024),
     'width' => $width,
     'height' => $height,
+    'md5sum' => $params['file_sum'],
     );
 
   $info_columns = array(
diff --git a/install/db/78-database.php b/install/db/78-database.php
new file mode 100644
index 000000000..7ab247512
--- /dev/null
+++ b/install/db/78-database.php
@@ -0,0 +1,46 @@
+<?php
+// +-----------------------------------------------------------------------+
+// | Piwigo - a PHP based picture gallery                                  |
+// +-----------------------------------------------------------------------+
+// | Copyright(C) 2008      Piwigo Team                  http://piwigo.org |
+// | Copyright(C) 2003-2008 PhpWebGallery Team    http://phpwebgallery.net |
+// | Copyright(C) 2002-2003 Pierrick LE GALL   http://le-gall.net/pierrick |
+// +-----------------------------------------------------------------------+
+// | This program is free software; you can redistribute it and/or modify  |
+// | it under the terms of the GNU General Public License as published by  |
+// | the Free Software Foundation                                          |
+// |                                                                       |
+// | This program is distributed in the hope that it will be useful, but   |
+// | WITHOUT ANY WARRANTY; without even the implied warranty of            |
+// | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU      |
+// | General Public License for more details.                              |
+// |                                                                       |
+// | You should have received a copy of the GNU General Public License     |
+// | along with this program; if not, write to the Free Software           |
+// | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, |
+// | USA.                                                                  |
+// +-----------------------------------------------------------------------+
+
+if (!defined('PHPWG_ROOT_PATH'))
+{
+  die('Hacking attempt!');
+}
+
+$upgrade_description = 'Add images.md5sum column, for web API uploaded photos';
+
+// +-----------------------------------------------------------------------+
+// |                            Upgrade content                            |
+// +-----------------------------------------------------------------------+
+
+$query = 'ALTER TABLE '.IMAGES_TABLE.' add column `md5sum` char(32) default NULL';
+pwg_query($query);
+
+$upgrade_description = $query;
+
+echo
+"\n"
+.'"'.$upgrade_description.'"'.' ended'
+."\n"
+;
+
+?>
diff --git a/install/piwigo_structure.sql b/install/piwigo_structure.sql
index 1ba00ca62..f4519839c 100644
--- a/install/piwigo_structure.sql
+++ b/install/piwigo_structure.sql
@@ -193,6 +193,7 @@ CREATE TABLE `piwigo_images` (
   `storage_category_id` smallint(5) unsigned default NULL,
   `high_filesize` mediumint(9) unsigned default NULL,
   `level` tinyint unsigned NOT NULL default '0',
+  `md5sum` char(32) default NULL,
   PRIMARY KEY  (`id`),
   KEY `images_i2` (`date_available`),
   KEY `images_i3` (`average_rate`),