diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 56a00b2419d..34d538675b9 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -2846,16 +2846,16 @@ class Product extends CommonObject
 	/**
 	 * Clone links between products
 	 *
-	 * @param 	int		$fromId		Product id
-	 * @param 	int		$toId		Product id
-	 * @return number
+	 * @param  int		$fromId		Product id
+	 * @param  int		$toId		Product id
+	 * @return int                  <0 if KO, >0 if OK
 	 */
 	function clone_associations($fromId, $toId)
 	{
 		$this->db->begin();
 
-		$sql = 'INSERT INTO '.MAIN_DB_PREFIX.'product_association (rowid, fk_product_pere, fk_product_fils, qty)';
-		$sql.= " SELECT null, $toId, fk_product_fils, qty FROM ".MAIN_DB_PREFIX."product_association";
+		$sql = 'INSERT INTO '.MAIN_DB_PREFIX.'product_association (fk_product_pere, fk_product_fils, qty)';
+		$sql.= " SELECT ".$toId.", fk_product_fils, qty FROM ".MAIN_DB_PREFIX."product_association";
 		$sql.= " WHERE fk_product_pere = '".$fromId."'";
 
 		dol_syslog(get_class($this).'::clone_association', LOG_DEBUG);