diff --git a/core/requires.js b/core/requires.js
index a55245b72..dc76807c4 100644
--- a/core/requires.js
+++ b/core/requires.js
@@ -83,3 +83,10 @@ goog.require('Blockly.FieldVariable');
 goog.require('Blockly.geras.Renderer');
 goog.require('Blockly.thrasos.Renderer');
 goog.require('Blockly.zelos.Renderer');
+
+// Blockly Themes.
+// Classic is the default theme.
+goog.require('Blockly.Themes.Classic');
+goog.require('Blockly.Themes.Dark');
+goog.require('Blockly.Themes.HighContrast');
+goog.require('Blockly.Themes.Modern');