diff --git a/core/designdocument.class.inc.php b/core/designdocument.class.inc.php
index a9448859d..ae873adba 100644
--- a/core/designdocument.class.inc.php
+++ b/core/designdocument.class.inc.php
@@ -77,6 +77,7 @@ class DesignDocument extends DOMDocument
 	 *
 	 * @return int
 	 */
+	#[\ReturnTypeWillChange]
 	public function save($filename, $options = 0)
 	{
 		$this->documentElement->setAttribute('xmlns:xsi', "http://www.w3.org/2001/XMLSchema-instance");
diff --git a/setup/modelfactory.class.inc.php b/setup/modelfactory.class.inc.php
index 3fd816f37..347a2e040 100644
--- a/setup/modelfactory.class.inc.php
+++ b/setup/modelfactory.class.inc.php
@@ -2538,6 +2538,7 @@ class MFDocument extends \Combodo\iTop\DesignDocument
 	 * @return string
 	 * @throws \Exception
 	 */
+	#[\ReturnTypeWillChange]
 	public function saveXML(DOMNode $node = null, $options = 0)
 	{
 		$oRootNode = $this->firstChild;