diff --git a/htdocs/contrat/class/contrat.class.php b/htdocs/contrat/class/contrat.class.php
index 78f97b3124a..29428ceb26d 100644
--- a/htdocs/contrat/class/contrat.class.php
+++ b/htdocs/contrat/class/contrat.class.php
@@ -3363,6 +3363,8 @@ class ContratLigne extends CommonObjectLine
 
 		// If we change a planned date (start or end), sync dates for all services
 		if (!$error && !empty($conf->global->CONTRACT_SYNC_PLANNED_DATE_OF_SERVICES)) {
+			dol_syslog(get_class($this)."::update CONTRACT_SYNC_PLANNED_DATE_OF_SERVICES is on so we update date for all lines", LOG_DEBUG);
+
 			if ($this->date_ouverture_prevue != $this->oldcopy->date_ouverture_prevue) {
 				$sql = 'UPDATE '.MAIN_DB_PREFIX.'contratdet SET';
 				$sql .= " date_ouverture_prevue = ".($this->date_ouverture_prevue != '' ? "'".$this->db->idate($this->date_ouverture_prevue)."'" : "null");