diff --git a/core/utils/toolbox.js b/core/utils/toolbox.js
index 1defda31c..c95e51dcb 100644
--- a/core/utils/toolbox.js
+++ b/core/utils/toolbox.js
@@ -16,6 +16,8 @@ goog.provide('Blockly.utils.toolbox');
 goog.requireType('Blockly.ToolboxCategory');
 goog.requireType('Blockly.ToolboxSeparator');
 
+goog.require("Blockly.constants");
+
 /**
  * The information needed to create a block in the toolbox.
  * @typedef {{