diff --git a/admin/site_reader_local.php b/admin/site_reader_local.php
index 79fac4b74..6ac43bf25 100644
--- a/admin/site_reader_local.php
+++ b/admin/site_reader_local.php
@@ -90,7 +90,7 @@ function get_elements($path)
 
       if (is_file($path.'/'.$node))
       {
-        $extension = get_extension($node);
+        $extension = strtolower(get_extension($node));
         $filename_wo_ext = get_filename_wo_extension($node);
 
         if ( isset($conf['flip_file_ext'][$extension]) )
diff --git a/include/config_default.inc.php b/include/config_default.inc.php
index a56e9fee7..65601c290 100644
--- a/include/config_default.inc.php
+++ b/include/config_default.inc.php
@@ -55,7 +55,7 @@
 
 // picture_ext : file extensions for picture file, must be a subset of
 // file_ext
-$conf['picture_ext'] = array('jpg','JPG','jpeg','JPEG','png','PNG','gif','GIF');
+$conf['picture_ext'] = array('jpg','jpeg','png','gif');
 
 // file_ext : file extensions (case sensitive) authorized
 $conf['file_ext'] = array_merge(
diff --git a/include/derivative.inc.php b/include/derivative.inc.php
index 8b65e8ad1..7ce84224c 100644
--- a/include/derivative.inc.php
+++ b/include/derivative.inc.php
@@ -54,7 +54,7 @@ final class SrcImage
     global $conf;
 
     $this->id = $infos['id'];
-    $ext = get_extension($infos['path']);
+    $ext = strtolower(get_extension($infos['path']));
     if (in_array($ext, $conf['picture_ext']))
     {
       $this->rel_path = $infos['path'];
@@ -66,7 +66,6 @@ final class SrcImage
     }
     else
     {
-      $ext = strtolower($ext);
       $this->rel_path = trigger_change('get_mimetype_location', get_themeconf('mime_icon_dir').$ext.'.png', $ext );
       $this->flags |= self::IS_MIMETYPE;
       if ( ($size=@getimagesize(PHPWG_ROOT_PATH.$this->rel_path)) === false)