diff --git a/code/TagField.php b/code/TagField.php
index 0103aad..fd6ca27 100644
--- a/code/TagField.php
+++ b/code/TagField.php
@@ -34,6 +34,11 @@ class TagField extends DropdownField {
 	 */
 	protected $titleField = 'Title';
 
+	/**
+	 * @var string
+	 */
+	protected $isMultiple;
+
 	/**
 	 * @param string $name
 	 * @param string $title