--- a/toolkit/components/extensions/LegacyExtensionsUtils.jsm
+++ b/toolkit/components/extensions/LegacyExtensionsUtils.jsm
@@ -12,16 +12,18 @@ this.EXPORTED_SYMBOLS = ["LegacyExtensio
  * This file exports helpers for Legacy Extensions that want to embed a webextensions
  * and exchange messages with the embedded WebExtension.
  */
 
 const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
+XPCOMUtils.defineLazyModuleGetter(this, "AsyncShutdown",
+                                  "resource://gre/modules/AsyncShutdown.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Extension",
                                   "resource://gre/modules/Extension.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "ExtensionChild",
                                   "resource://gre/modules/ExtensionChild.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Services",
                                   "resource://gre/modules/Services.jsm");
 
 Cu.import("resource://gre/modules/ExtensionCommon.jsm");
@@ -200,19 +202,25 @@ class EmbeddedExtension {
    *
    * @returns {Promise<void>} a promise that is resolved when the shutdown has been done
    */
   shutdown() {
     EmbeddedExtensionManager.untrackEmbeddedExtension(this);
 
     // If there is a pending startup,  wait to be completed and then shutdown.
     if (this.startupPromise) {
-      return this.startupPromise.then(() => {
-        this.extension.shutdown();
+      let promise = this.startupPromise.then(() => {
+        return this.extension.shutdown();
       });
+
+      AsyncShutdown.profileChangeTeardown.addBlocker(
+        `Legacy Extension Shutdown: ${this.addonId}`,
+        promise.catch(() => {}));
+
+      return promise;
     }
 
     // Run shutdown now if the embedded webextension has been correctly started
     if (this.extension && this.started && !this.extension.hasShutdown) {
       this.extension.shutdown();
     }
 
     return Promise.resolve();