diff --git a/api/src/Etemplate/Widget/File.php b/api/src/Etemplate/Widget/File.php
index 06caef931a..add9a199e9 100644
--- a/api/src/Etemplate/Widget/File.php
+++ b/api/src/Etemplate/Widget/File.php
@@ -41,7 +41,7 @@ class File extends Etemplate\Widget
 	 */
 	public function __construct($xml='')
 	{
-		$this->bool_attr_default += array(
+		$this->bool_attr_default = ($this->bool_attr_default ?? []) + array(
 			'multiple' => false,
 		);