diff --git a/htdocs/contrat/card.php b/htdocs/contrat/card.php
index 802305b6306..b691524ad92 100644
--- a/htdocs/contrat/card.php
+++ b/htdocs/contrat/card.php
@@ -694,6 +694,8 @@ if (empty($reshook)) {
 				$error++;
 			}
 			$objectline->fetch_optionals();
+
+			$objectline->oldcopy = dol_clone($objectline);
 		}
 
 		$db->begin();
diff --git a/htdocs/contrat/class/contrat.class.php b/htdocs/contrat/class/contrat.class.php
index 5c72bf51c69..7d43da46b37 100644
--- a/htdocs/contrat/class/contrat.class.php
+++ b/htdocs/contrat/class/contrat.class.php
@@ -3392,7 +3392,7 @@ class ContratLigne extends CommonObjectLine
 			}
 		}
 
-		// If we change a planned date (start or end), sync dates for all services
+		// If we change a planned date (start or end) of one contract line, sync dates for all other services too
 		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);
 
diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 0bf63ee9b0b..160dd0b7575 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -1160,26 +1160,26 @@ function dol_buildpath($path, $type = 0, $returnemptyifnotfound = 0)
 
 /**
  *	Create a clone of instance of object (new instance with same value for properties)
- *  With native = 0: Property that are reference are also new object (full isolation clone). This means $this->db of new object is not valid.
+ *  With native = 0: Property that are reference are also new object (full isolation clone). This means $this->db of new object may not be valid.
  *  With native = 1: Use PHP clone. Property that are reference are same pointer. This means $this->db of new object is still valid but point to same this->db than original object.
  *
  * 	@param	object	$object		Object to clone
- *  @param	int		$native		0=Full isolation method, 1=Native PHP method
+ *  @param	int		$native		0=Full isolation method, 1=Native PHP method, 2=Full isolation method+destroy non scalar or array properties (recommended)
  *	@return object				Clone object
  *  @see https://php.net/manual/language.oop5.cloning.php
  */
 function dol_clone($object, $native = 0)
 {
-	if (empty($native)) {
+	if ($native == 0) {
 		$tmpsavdb = null;
 		if (isset($object->db) && isset($object->db->db) && is_object($object->db->db) && get_class($object->db->db) == 'PgSql\Connection') {
 			$tmpsavdb = $object->db;
-			unset($object->db);		// Such property can not be serialized when PgSql/Connection
+			unset($object->db);		// Such property can not be serialized with pgsl (when object->db->db = 'PgSql\Connection')
 		}
 
 		$myclone = unserialize(serialize($object));	// serialize then unserialize is hack to be sure to have a new object for all fields
 
-		if ($tmpsavdb) {
+		if (!empty($tmpsavdb)) {
 			$object->db = $tmpsavdb;
 		}
 	} else {