diff --git CHANGELOG.txt CHANGELOG.txt
index 1d1b1e4..89b5c54 100644
--- CHANGELOG.txt
+++ CHANGELOG.txt
@@ -1,5 +1,8 @@
 // $Id$
 
+amazon_store-7.x-???
+[#878048] by the_g_bomb: Fix cart-add confirmation message.
+
 amazon_store-6.x-2.0-RC2
 ------------------------
 [#764116] by rfay: Implement a real pager for search results!
diff --git amazon_store.module amazon_store.module
index 0bd6d90..072ebd4 100644
--- amazon_store.module
+++ amazon_store.module
@@ -720,8 +720,11 @@ function amazon_store_update_cart_quantity($cartItemId, $quantity ) {
   );
 
   $results = amazon_store_http_request('CartModify', $parameters);
-  $actual_quantity = $quantity > 0 ? (int) $results->Cart->CartItems->CartItem[0]->Quantity : $quantity;
-
+  foreach ($results->Cart->CartItems->CartItem as $cartitem) {
+    if ($cartitem->CartItemId == $cartItemId) {
+      $actual_quantity = $quantity > 0 ? (int)$cartitem->Quantity : $quantity;
+    }
+  }
   if (empty($results->error)) {
     drupal_set_message(t("Cart quantity updated to @quantity", array('@quantity' => $actual_quantity)));
     return TRUE;