diff --git a/core/interfaces/i_flyout.js b/core/interfaces/i_flyout.js
index b819c3347..7a05fb9da 100644
--- a/core/interfaces/i_flyout.js
+++ b/core/interfaces/i_flyout.js
@@ -11,7 +11,8 @@
 
 'use strict';
 
-goog.provide('Blockly.IFlyout');
+goog.module('Blockly.IFlyout');
+goog.module.declareLegacyNamespace();
 
 goog.requireType('Blockly.BlockSvg');
 goog.requireType('Blockly.IRegistrable');
@@ -26,45 +27,45 @@ goog.requireType('Blockly.WorkspaceSvg');
  * @extends {Blockly.IRegistrable}
  * @interface
  */
-Blockly.IFlyout = function() {};
+const IFlyout = function() {};
 
 /**
  * Whether the flyout is laid out horizontally or not.
  * @type {boolean}
  */
-Blockly.IFlyout.prototype.horizontalLayout;
+IFlyout.prototype.horizontalLayout;
 
 /**
  * Is RTL vs LTR.
  * @type {boolean}
  */
-Blockly.IFlyout.prototype.RTL;
+IFlyout.prototype.RTL;
 
 /**
  * The target workspace
  * @type {?Blockly.WorkspaceSvg}
  */
-Blockly.IFlyout.prototype.targetWorkspace;
+IFlyout.prototype.targetWorkspace;
 
 /**
  * Margin around the edges of the blocks in the flyout.
  * @type {number}
  * @const
  */
-Blockly.IFlyout.prototype.MARGIN;
+IFlyout.prototype.MARGIN;
 
 /**
  * Does the flyout automatically close when a block is created?
  * @type {boolean}
  */
-Blockly.IFlyout.prototype.autoClose;
+IFlyout.prototype.autoClose;
 
 /**
  * Corner radius of the flyout background.
  * @type {number}
  * @const
  */
-Blockly.IFlyout.prototype.CORNER_RADIUS;
+IFlyout.prototype.CORNER_RADIUS;
 
 /**
  * Creates the flyout's DOM.  Only needs to be called once.  The flyout can
@@ -76,62 +77,62 @@ Blockly.IFlyout.prototype.CORNER_RADIUS;
  *     put the flyout in. This should be <svg> or <g>.
  * @return {!SVGElement} The flyout's SVG group.
  */
-Blockly.IFlyout.prototype.createDom;
+IFlyout.prototype.createDom;
 
 /**
  * Initializes the flyout.
  * @param {!Blockly.WorkspaceSvg} targetWorkspace The workspace in which to
  *     create new blocks.
  */
-Blockly.IFlyout.prototype.init;
+IFlyout.prototype.init;
 
 /**
  * Dispose of this flyout.
  * Unlink from all DOM elements to prevent memory leaks.
  */
-Blockly.IFlyout.prototype.dispose;
+IFlyout.prototype.dispose;
 
 /**
  * Get the width of the flyout.
  * @return {number} The width of the flyout.
  */
-Blockly.IFlyout.prototype.getWidth;
+IFlyout.prototype.getWidth;
 
 /**
  * Get the height of the flyout.
  * @return {number} The width of the flyout.
  */
-Blockly.IFlyout.prototype.getHeight;
+IFlyout.prototype.getHeight;
 
 /**
  * Get the workspace inside the flyout.
  * @return {!Blockly.WorkspaceSvg} The workspace inside the flyout.
  */
-Blockly.IFlyout.prototype.getWorkspace;
+IFlyout.prototype.getWorkspace;
 
 /**
  * Is the flyout visible?
  * @return {boolean} True if visible.
  */
-Blockly.IFlyout.prototype.isVisible;
+IFlyout.prototype.isVisible;
 
 /**
  * Set whether the flyout is visible. A value of true does not necessarily mean
  * that the flyout is shown. It could be hidden because its container is hidden.
  * @param {boolean} visible True if visible.
  */
-Blockly.IFlyout.prototype.setVisible;
+IFlyout.prototype.setVisible;
 
 /**
  * Set whether this flyout's container is visible.
  * @param {boolean} visible Whether the container is visible.
  */
-Blockly.IFlyout.prototype.setContainerVisible;
+IFlyout.prototype.setContainerVisible;
 
 /**
  * Hide and empty the flyout.
  */
-Blockly.IFlyout.prototype.hide;
+IFlyout.prototype.hide;
 
 /**
  * Show and populate the flyout.
@@ -139,7 +140,7 @@ Blockly.IFlyout.prototype.hide;
  *     display in the flyout. This is either an array of Nodes, a NodeList, a
  *     toolbox definition, or a string with the name of the dynamic category.
  */
-Blockly.IFlyout.prototype.show;
+IFlyout.prototype.show;
 
 /**
  * Create a copy of this block on the workspace.
@@ -147,36 +148,36 @@ Blockly.IFlyout.prototype.show;
  * @return {!Blockly.BlockSvg} The newly created block.
  * @throws {Error} if something went wrong with deserialization.
  */
-Blockly.IFlyout.prototype.createBlock;
+IFlyout.prototype.createBlock;
 
 /**
  * Reflow blocks and their mats.
  */
-Blockly.IFlyout.prototype.reflow;
+IFlyout.prototype.reflow;
 
 /**
  * @return {boolean} True if this flyout may be scrolled with a scrollbar or by
  *     dragging.
  */
-Blockly.IFlyout.prototype.isScrollable;
+IFlyout.prototype.isScrollable;
 
 /**
  * Calculates the x coordinate for the flyout position.
  * @return {number} X coordinate.
  */
-Blockly.IFlyout.prototype.getX;
+IFlyout.prototype.getX;
 
 /**
  * Calculates the y coordinate for the flyout position.
  * @return {number} Y coordinate.
  */
-Blockly.IFlyout.prototype.getY;
+IFlyout.prototype.getY;
 
 /**
  * Position the flyout.
  * @return {void}
  */
-Blockly.IFlyout.prototype.position;
+IFlyout.prototype.position;
 
 /**
  * Determine if a drag delta is toward the workspace, based on the position
@@ -186,4 +187,6 @@ Blockly.IFlyout.prototype.position;
  *     moved from the position at mouse down, in pixel units.
  * @return {boolean} True if the drag is toward the workspace.
  */
-Blockly.IFlyout.prototype.isDragTowardWorkspace;
+IFlyout.prototype.isDragTowardWorkspace;
+
+exports = IFlyout;
diff --git a/tests/deps.js b/tests/deps.js
index b4d64e1fa..3163a584c 100644
--- a/tests/deps.js
+++ b/tests/deps.js
@@ -88,7 +88,7 @@ goog.addDependency('../../core/interfaces/i_deletable.js', ['Blockly.IDeletable'
 goog.addDependency('../../core/interfaces/i_delete_area.js', ['Blockly.IDeleteArea'], ['Blockly.IDragTarget'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/interfaces/i_drag_target.js', ['Blockly.IDragTarget'], ['Blockly.IComponent'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/interfaces/i_draggable.js', ['Blockly.IDraggable'], ['Blockly.IDeletable'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../core/interfaces/i_flyout.js', ['Blockly.IFlyout'], []);
+goog.addDependency('../../core/interfaces/i_flyout.js', ['Blockly.IFlyout'], [], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/interfaces/i_keyboard_accessible.js', ['Blockly.IKeyboardAccessible'], [], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../core/interfaces/i_metrics_manager.js', ['Blockly.IMetricsManager'], []);
 goog.addDependency('../../core/interfaces/i_movable.js', ['Blockly.IMovable'], [], {'lang': 'es6', 'module': 'goog'});