diff --git a/core/events/events_viewport.js b/core/events/events_viewport.js
index 6d857cd67..2cfd94a7f 100644
--- a/core/events/events_viewport.js
+++ b/core/events/events_viewport.js
@@ -10,12 +10,13 @@
  */
 'use strict';
 
-goog.provide('Blockly.Events.ViewportChange');
+goog.module('Blockly.Events.ViewportChange');
+goog.module.declareLegacyNamespace();
 
-goog.require('Blockly.Events');
-goog.require('Blockly.Events.UiBase');
-goog.require('Blockly.registry');
-goog.require('Blockly.utils.object');
+const Events = goog.require('Blockly.Events');
+const UiBase = goog.require('Blockly.Events.UiBase');
+const object = goog.require('Blockly.utils.object');
+const registry = goog.require('Blockly.registry');
 
 
 /**
@@ -30,12 +31,12 @@ goog.require('Blockly.utils.object');
  *    Undefined for a blank event.
  * @param {number=} opt_oldScale The old scale of the workspace. Undefined for a
  *    blank event.
- * @extends {Blockly.Events.UiBase}
+ * @extends {UiBase}
  * @constructor
  */
-Blockly.Events.ViewportChange = function(opt_top, opt_left, opt_scale,
-    opt_workspaceId, opt_oldScale) {
-  Blockly.Events.ViewportChange.superClass_.constructor.call(this, opt_workspaceId);
+const ViewportChange = function(
+    opt_top, opt_left, opt_scale, opt_workspaceId, opt_oldScale) {
+  ViewportChange.superClass_.constructor.call(this, opt_workspaceId);
 
   /**
    * Top-edge of the visible portion of the workspace, relative to the workspace
@@ -63,21 +64,20 @@ Blockly.Events.ViewportChange = function(opt_top, opt_left, opt_scale,
    */
   this.oldScale = opt_oldScale;
 };
-Blockly.utils.object.inherits(Blockly.Events.ViewportChange,
-    Blockly.Events.UiBase);
+object.inherits(ViewportChange, UiBase);
 
 /**
  * Type of this event.
  * @type {string}
  */
-Blockly.Events.ViewportChange.prototype.type = Blockly.Events.VIEWPORT_CHANGE;
+ViewportChange.prototype.type = Events.VIEWPORT_CHANGE;
 
 /**
  * Encode the event as JSON.
  * @return {!Object} JSON representation.
  */
-Blockly.Events.ViewportChange.prototype.toJson = function() {
-  var json = Blockly.Events.ViewportChange.superClass_.toJson.call(this);
+ViewportChange.prototype.toJson = function() {
+  const json = ViewportChange.superClass_.toJson.call(this);
   json['viewTop'] = this.viewTop;
   json['viewLeft'] = this.viewLeft;
   json['scale'] = this.scale;
@@ -89,13 +89,14 @@ Blockly.Events.ViewportChange.prototype.toJson = function() {
  * Decode the JSON event.
  * @param {!Object} json JSON representation.
  */
-Blockly.Events.ViewportChange.prototype.fromJson = function(json) {
-  Blockly.Events.ViewportChange.superClass_.fromJson.call(this, json);
+ViewportChange.prototype.fromJson = function(json) {
+  ViewportChange.superClass_.fromJson.call(this, json);
   this.viewTop = json['viewTop'];
   this.viewLeft = json['viewLeft'];
   this.scale = json['scale'];
   this.oldScale = json['oldScale'];
 };
 
-Blockly.registry.register(Blockly.registry.Type.EVENT,
-    Blockly.Events.VIEWPORT_CHANGE, Blockly.Events.ViewportChange);
+registry.register(registry.Type.EVENT, Events.VIEWPORT_CHANGE, ViewportChange);
+
+exports = ViewportChange;
diff --git a/tests/deps.js b/tests/deps.js
index 62654bfa4..03c4b65e5 100644
--- a/tests/deps.js
+++ b/tests/deps.js
@@ -44,7 +44,7 @@ goog.addDependency('../../core/events/events_selected.js', ['Blockly.Events.Sele
 goog.addDependency('../../core/events/events_theme_change.js', ['Blockly.Events.ThemeChange'], ['Blockly.Events', 'Blockly.Events.UiBase', 'Blockly.registry', 'Blockly.utils.object']);
 goog.addDependency('../../core/events/events_toolbox_item_select.js', ['Blockly.Events.ToolboxItemSelect'], ['Blockly.Events', 'Blockly.Events.UiBase', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/events_trashcan_open.js', ['Blockly.Events.TrashcanOpen'], ['Blockly.Events', 'Blockly.Events.UiBase', 'Blockly.registry', 'Blockly.utils.object']);
-goog.addDependency('../../core/events/events_viewport.js', ['Blockly.Events.ViewportChange'], ['Blockly.Events', 'Blockly.Events.UiBase', 'Blockly.registry', 'Blockly.utils.object']);
+goog.addDependency('../../core/events/events_viewport.js', ['Blockly.Events.ViewportChange'], ['Blockly.Events', 'Blockly.Events.UiBase', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/events/ui_events.js', ['Blockly.Events.Ui', 'Blockly.Events.UiBase'], ['Blockly.Events', 'Blockly.Events.Abstract', 'Blockly.registry', 'Blockly.utils.object']);
 goog.addDependency('../../core/events/variable_events.js', ['Blockly.Events.VarBase', 'Blockly.Events.VarCreate', 'Blockly.Events.VarDelete', 'Blockly.Events.VarRename'], ['Blockly.Events', 'Blockly.Events.Abstract', 'Blockly.registry', 'Blockly.utils.object']);
 goog.addDependency('../../core/events/workspace_events.js', ['Blockly.Events.FinishedLoading'], ['Blockly.Events', 'Blockly.Events.Abstract', 'Blockly.registry', 'Blockly.utils.object'], {'lang': 'es5'});