diff --git a/core/theme/zelos.js b/core/theme/zelos.js
index 361b9e4d0..bfb2d0768 100644
--- a/core/theme/zelos.js
+++ b/core/theme/zelos.js
@@ -9,15 +9,16 @@
  */
 'use strict';
 
-goog.provide('Blockly.Themes.Zelos');
+goog.module('Blockly.Themes.Zelos');
+goog.module.declareLegacyNamespace();
 
 goog.require('Blockly.Theme');
 
 
 // Temporary holding object.
-Blockly.Themes.Zelos = {};
+let Zelos = {};
 
-Blockly.Themes.Zelos.defaultBlockStyles = {
+Zelos.defaultBlockStyles = {
   "colour_blocks": {
     "colourPrimary": "#CF63CF",
     "colourSecondary": "#C94FC9",
@@ -71,7 +72,7 @@ Blockly.Themes.Zelos.defaultBlockStyles = {
   }
 };
 
-Blockly.Themes.Zelos.categoryStyles = {
+Zelos.categoryStyles = {
   "colour_category": {
     "colour": "#CF63CF"
   },
@@ -101,6 +102,8 @@ Blockly.Themes.Zelos.categoryStyles = {
   }
 };
 
-Blockly.Themes.Zelos =
-    new Blockly.Theme('zelos', Blockly.Themes.Zelos.defaultBlockStyles,
-        Blockly.Themes.Zelos.categoryStyles);
+Zelos =
+    new Blockly.Theme('zelos', Zelos.defaultBlockStyles,
+        Zelos.categoryStyles);
+
+exports = Zelos;
diff --git a/tests/deps.js b/tests/deps.js
index a213beb75..8e1c3d6fb 100644
--- a/tests/deps.js
+++ b/tests/deps.js
@@ -192,7 +192,7 @@ goog.addDependency('../../core/shortcut_items.js', ['Blockly.ShortcutItems'], ['
 goog.addDependency('../../core/shortcut_registry.js', ['Blockly.ShortcutRegistry'], ['Blockly.utils.KeyCodes', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/theme.js', ['Blockly.Theme'], ['Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/theme/classic.js', ['Blockly.Themes.Classic'], ['Blockly.Theme']);
-goog.addDependency('../../core/theme/zelos.js', ['Blockly.Themes.Zelos'], ['Blockly.Theme']);
+goog.addDependency('../../core/theme/zelos.js', ['Blockly.Themes.Zelos'], ['Blockly.Theme'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/theme_manager.js', ['Blockly.ThemeManager'], ['Blockly.utils.dom'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/toolbox/category.js', ['Blockly.ToolboxCategory'], ['Blockly', 'Blockly.Css', 'Blockly.ToolboxItem', 'Blockly.registry', 'Blockly.utils', 'Blockly.utils.aria', 'Blockly.utils.dom', 'Blockly.utils.object', 'Blockly.utils.toolbox'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/toolbox/collapsible_category.js', ['Blockly.CollapsibleToolboxCategory'], ['Blockly.ToolboxCategory', 'Blockly.ToolboxSeparator', 'Blockly.registry', 'Blockly.utils.aria', 'Blockly.utils.dom', 'Blockly.utils.object', 'Blockly.utils.toolbox'], {'lang': 'es6', 'module': 'goog'});