diff --git a/src/opnsense/mvc/app/models/OPNsense/Base/FieldTypes/BaseListField.php b/src/opnsense/mvc/app/models/OPNsense/Base/FieldTypes/BaseListField.php
index a0efa063b..89addec8a 100644
--- a/src/opnsense/mvc/app/models/OPNsense/Base/FieldTypes/BaseListField.php
+++ b/src/opnsense/mvc/app/models/OPNsense/Base/FieldTypes/BaseListField.php
@@ -58,6 +58,11 @@ abstract class BaseListField extends BaseField
      */
     private $internalMultiSelect = false;
 
+    /**
+     * @var string default validation message string
+     */
+    protected $internalValidationMessage = "option not in list";
+
     /**
      * select if multiple interfaces may be selected at once
      * @param $value boolean value 0/1