diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 6a615ce01c2..e1fb258f11e 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -338,7 +338,7 @@ class Product extends CommonObject
 				$sql.= ", ".$this->status;
 				$sql.= ", ".$this->status_buy;
 				$sql.= ", '".$this->canvas."'";
-				$sql.= ", ".((! isset($this->finished) || $this->finished < 0)?'null':$this->finished);
+				$sql.= ", ".((! isset($this->finished) || $this->finished < 0 || $this->finished == '') ? 'null' : $this->finished);
 				$sql.= ")";
 
 				dol_syslog(get_class($this)."::Create sql=".$sql);