diff --git a/code/StringTagField.php b/code/StringTagField.php
index 38ce4af..18785d1 100644
--- a/code/StringTagField.php
+++ b/code/StringTagField.php
@@ -32,6 +32,11 @@ class StringTagField extends DropdownField {
 	 */
 	protected $record;
 
+	/**
+	 * @var boolean
+	 */
+	protected $isMultiple;
+
 	/**
 	 * @param string $name
 	 * @param string $title