diff --git a/htdocs/product/class/api_products.class.php b/htdocs/product/class/api_products.class.php
index 37c950e9956..b0ed902ffb3 100644
--- a/htdocs/product/class/api_products.class.php
+++ b/htdocs/product/class/api_products.class.php
@@ -1328,11 +1328,12 @@ class Products extends DolibarrApi
      *
      * "features" is a list of attributes pairs id_attribute=>id_value. Example: array(id_color=>id_Blue, id_size=>id_small, id_option=>id_val_a, ...)
      *
-     * @param  int    $id                       ID of Product
-     * @param  float  $weight_impact            Weight impact of variant
-     * @param  float  $price_impact             Price impact of variant
-     * @param  bool   $price_impact_is_percent  Price impact in percent (true or false)
-     * @param  array  $features                 List of attributes pairs id_attribute->id_value. Example: array(id_color=>id_Blue, id_size=>id_small, id_option=>id_val_a, ...)
+     * @param  int $id ID of Product
+     * @param  float $weight_impact Weight impact of variant
+     * @param  float $price_impact Price impact of variant
+     * @param  bool $price_impact_is_percent Price impact in percent (true or false)
+     * @param  array $features List of attributes pairs id_attribute->id_value. Example: array(id_color=>id_Blue, id_size=>id_small, id_option=>id_val_a, ...)
+     * @param  bool|string $reference Customized reference of variant
      * @return int
      *
      * @throws RestException
@@ -1341,7 +1342,7 @@ class Products extends DolibarrApi
      *
      * @url POST {id}/variants
      */
-    public function addVariant($id, $weight_impact, $price_impact, $price_impact_is_percent, $features)
+    public function addVariant($id, $weight_impact, $price_impact, $price_impact_is_percent, $features, $reference = false)
     {
         if(! DolibarrApiAccess::$user->rights->produit->creer) {
             throw new RestException(401);
@@ -1373,7 +1374,7 @@ class Products extends DolibarrApi
         $prodcomb = new ProductCombination($this->db);
         if (! $prodcomb->fetchByProductCombination2ValuePairs($id, $features))
         {
-            $result = $prodcomb->createProductCombination(DolibarrApiAccess::$user, $this->product, $features, array(), $price_impact_is_percent, $price_impact, $weight_impact);
+            $result = $prodcomb->createProductCombination(DolibarrApiAccess::$user, $this->product, $features, array(), $price_impact_is_percent, $price_impact, $weight_impact, $reference);
             if ($result > 0)
             {
                 return $result;