diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 96a8d9fc59d..24ed27c5bf7 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -1273,7 +1273,7 @@ class Product extends CommonObject
 			$sql .= ", sell_or_eat_by_mandatory = ".((empty($this->sell_or_eat_by_mandatory) || $this->sell_or_eat_by_mandatory < 0) ? 0 : (int) $this->sell_or_eat_by_mandatory);
 			$sql .= ", batch_mask = '".$this->db->escape($this->batch_mask)."'";
 
-			$sql .= ", finished = ".((!isset($this->finished) || $this->finished < 0 || $this->finished == '') ? "null" : (int) $this->finished);
+			$sql .= ", finished = ".((!isset($this->finished) || $this->finished < 0 || $this->finished === '') ? "null" : (int) $this->finished);
 			$sql .= ", fk_default_bom = ".((!isset($this->fk_default_bom) || $this->fk_default_bom < 0 || $this->fk_default_bom == '') ? "null" : (int) $this->fk_default_bom);
 			$sql .= ", net_measure = ".($this->net_measure != '' ? "'".$this->db->escape($this->net_measure)."'" : 'null');
 			$sql .= ", net_measure_units = ".($this->net_measure_units != '' ? "'".$this->db->escape($this->net_measure_units)."'" : 'null');