diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index 55abcee5699..1a8f7bc7bb9 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -6221,7 +6221,7 @@ abstract class CommonObject
 			if (! empty($this->fields[$key]['foreignkey']) && $values[$key] == '-1') $values[$key]='';
 
 			//var_dump($key.'-'.$values[$key].'-'.($this->fields[$key]['notnull'] == 1));
-			if ($this->fields[$key]['notnull'] == 1 && empty($values[$key]))
+			if ($this->fields[$key]['notnull'] == 1 && ! isset($values[$key]))
 			{
 				$error++;
 				$this->errors[]=$langs->trans("ErrorFieldRequired", $this->fields[$key]['label']);