diff --git a/src/experiment_apis/customizableUI/api.js b/src/experiment_apis/customizableUI/api.js
index 50f6159..d95270d 100644
--- a/src/experiment_apis/customizableUI/api.js
+++ b/src/experiment_apis/customizableUI/api.js
@@ -1,14 +1,14 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-/* global ChromeUtils ExtensionAPI ExtensionCommon */
+/* global ChromeUtils ExtensionAPI */
 
 this.customizableUI = class extends ExtensionAPI {
   getAPI(context) {
-    const {Services} = ChromeUtils.import('resource://gre/modules/Services.jsm');
-    ChromeUtils.import('resource://gre/modules/ExtensionCommon.jsm');
+    const {CustomizableUI} = ChromeUtils.import('resource:///modules/CustomizableUI.jsm');
+    const {ExtensionCommon} = ChromeUtils.import('resource://gre/modules/ExtensionCommon.jsm');
     const {EventManager} = ExtensionCommon;
-    const {CustomizableUI} = ChromeUtils.import('resource:///modules/CustomizableUI.jsm', {});
+    const {Services} = ChromeUtils.import('resource://gre/modules/Services.jsm');
     return {
       customizableUI: {
         onWidgetRemoved: new EventManager(
@@ -27,8 +27,12 @@ this.customizableUI = class extends ExtensionAPI {
           },
         ).api(),
         async isWidgetInOverflow(widgetId) {
+          const {area} = CustomizableUI.getPlacementOfWidget(widgetId);
           const browserWindow = Services.wm.getMostRecentWindow('navigator:browser');
-          return CustomizableUI.getWidget(widgetId).forWindow(browserWindow).overflowed;
+          // First check is for the non-fixed overflow menu (e.g. widget moved by resizing window)
+          // Second is for fixed overflow menu (e.g. widget moved by (un)pinning button to overflow)
+          return (CustomizableUI.getWidget(widgetId).forWindow(browserWindow).overflowed
+            || area === 'widget-overflow-fixed-list');
         },
       },
     };
diff --git a/src/experiment_apis/customizableUI/schema.json b/src/experiment_apis/customizableUI/schema.json
index 6179b04..63a7c9f 100644
--- a/src/experiment_apis/customizableUI/schema.json
+++ b/src/experiment_apis/customizableUI/schema.json
@@ -5,7 +5,7 @@
       {
         "name": "onWidgetRemoved",
         "type": "function",
-        "description": "Fired when a widget is removed from the browser chrome",
+        "description": "Fired when a widget is removed from the browser chrome.",
         "parameters": [
           {
             "name": "widgetId",
@@ -19,7 +19,7 @@
       {
         "name": "isWidgetInOverflow",
         "type": "function",
-        "description": "Returns a boolean for whether or not the provided widget in the provided window is in the overflow menu or not.",
+        "description": "Determine whether or not a widget is in the overflow menu.",
         "async": true,
         "parameters": [
           {