diff --git a/htdocs/core/class/commondocgenerator.class.php b/htdocs/core/class/commondocgenerator.class.php
index 99c8bf820493f..3792aaf932710 100644
--- a/htdocs/core/class/commondocgenerator.class.php
+++ b/htdocs/core/class/commondocgenerator.class.php
@@ -33,7 +33,11 @@
  */
 abstract class CommonDocGenerator
 {
-	var $error='';
+	/**
+	 * @var string Error code (or message)
+	 */
+	public $error='';
+
 	protected $db;