--- feeds_tamper.module.orig	2013-03-10 21:22:52.000000000 +0200
+++ feeds_tamper.module	2013-04-24 17:24:10.186018080 +0300
@@ -34,15 +34,23 @@
   $blank_mappings = array();
 
   foreach ($importer_instances as $element_key => $instance) {
+    $element_key_lowercase = drupal_strtolower($element_key);
     if (strpos($element_key, 'Blank source ') === 0) {
-      $blank_mappings[] = $element_key;
+      $blank_mappings[] = $csv ? $element_key_lowercase : $element_key;
     }
     // Special case for FeedsCSVParser.
-    elseif ($csv) {
+    if ($csv) {
       unset($importer_instances[$element_key]);
-      $importer_instances[drupal_strtolower($element_key)] = $instance;
+      $importer_instances[$element_key_lowercase] = $instance;
     }
+
+  }
+
+  $mappings_uniq_names = array();
+  foreach($mappings as $maps_item) {
+    $mappings_uniq_names[] = drupal_strtolower($maps_item['source']);
   }
+  $mappings_uniq_names = array_unique($mappings_uniq_names);
 
   $plugins = feeds_tamper_get_plugins();
   foreach ($result->items as $item_key => &$item) {
@@ -50,7 +58,10 @@
     foreach ($blank_mappings as $blank) {
       $item[$blank] = '';
     }
-    foreach ($importer_instances as $element_key => $instances) {
+
+    foreach ($mappings_uniq_names as $element_key) {
+      $instances = $importer_instances[$element_key];
+
       if (isset($item[$element_key])) {
         foreach ($instances as $instance) {
           $plugin = $plugins[$instance->plugin_id];