diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index d557dd90392..a202004ed02 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -3603,7 +3603,7 @@ class Product extends CommonObject
 
     	$sql = "SELECT sum(d.qty), date_format(d.date_valid, '%Y%m')";
     	if ($mode == 'bynumber') {
-    		$sql .= ", count(DISTINCT c.rowid)";
+    		$sql .= ", count(DISTINCT d.rowid)";
     	}
     	$sql .= " FROM ".MAIN_DB_PREFIX."mrp_mo as d LEFT JOIN  ".MAIN_DB_PREFIX."societe as s ON d.fk_soc = s.rowid";
     	if ($filteronproducttype >= 0) {