diff --git a/htdocs/contrat/class/contrat.class.php b/htdocs/contrat/class/contrat.class.php
index 24b51e835a2..52bc7efd860 100644
--- a/htdocs/contrat/class/contrat.class.php
+++ b/htdocs/contrat/class/contrat.class.php
@@ -872,7 +872,7 @@ class Contrat extends CommonObject
 		$sql.= " fk_commercial_signature, fk_commercial_suivi, fk_projet,";
 		$sql.= " ref, entity, note_private, note_public, ref_customer, ref_supplier, ref_ext)";
 		$sql.= " VALUES ('".$this->db->idate($now)."',".$this->socid.",".$user->id;
-		$sql.= ", '".$this->db->idate($this->date_contrat)."'";
+		$sql.= ", ".(dol_strlen($this->date_contrat)!=0 ? "'".$this->db->idate($this->date_contrat)."'" : "NULL");
 		$sql.= ",".($this->commercial_signature_id>0?$this->commercial_signature_id:"NULL");
 		$sql.= ",".($this->commercial_suivi_id>0?$this->commercial_suivi_id:"NULL");
 		$sql.= ",".($this->fk_project>0?$this->fk_project:"NULL");