diff --git a/webext/js/folderChange.js b/webext/js/folderChange.js
index 43bfbc0..370163a 100644
--- a/webext/js/folderChange.js
+++ b/webext/js/folderChange.js
@@ -56,15 +56,15 @@ var folderChange = class extends ExtensionCommon.ExtensionAPI {
     return {
       // Again, this key must have the same name.
       folderChange: {
-        setVersion: function (version) {
+        setVersion: async function (version) {
           SysTrayX.setVersion(version);
         },
 
-        setCountType: function (type) {
+        setCountType: async function (type) {
           SysTrayX.setCountType(type);
         },
 
-        setFilters: function (filters) {
+        setFilters: async function (filters) {
           SysTrayX.setFilters(filters);
         },
 
diff --git a/webext/js/windowEvent.js b/webext/js/windowEvent.js
index 681ab6d..d84f811 100644
--- a/webext/js/windowEvent.js
+++ b/webext/js/windowEvent.js
@@ -1,36 +1,4 @@
-/* eslint-disable object-shorthand */
-
-// Get various parts of the WebExtension framework that we need.
-var { ExtensionCommon } = ChromeUtils.import(
-  "resource://gre/modules/ExtensionCommon.jsm"
-);
-
-// You probably already know what this does.
-var { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-
-// ChromeUtils.import() works in experiments for core resource urls as it did
-// in legacy add-ons. However, chrome:// urls that point to add-on resources no
-// longer work, as the "chrome.manifest" file is no longer supported, which
-// defined the root path for each add-on. Instead, ChromeUtils.import() needs
-// a url generated by
-//
-// let url = context.extension.rootURI.resolve("path/to/file.jsm")
-//
-// Instead of taking the extension object from the context, you may generate
-// the extension object from a given add-on ID as shown in the example below.
-// This allows to import a JSM without context, for example inside another JSM.
-//
-var { ExtensionParent } = ChromeUtils.import(
-  "resource://gre/modules/ExtensionParent.jsm"
-);
-var extension = ExtensionParent.GlobalManager.getExtension(
-  "systray-x@Ximi1970"
-);
-var { windowEvent } = ChromeUtils.import(
-  extension.rootURI.resolve("modules/windowEvent.jsm")
-);
-
-// This is the important part. It implements the functions and events defined in schema.json.
+/// This is the important part. It implements the functions and events defined in schema.json.
 // The variable must have the same name you've been using so far, "myapi" in this case.
 var windowEvent = class extends ExtensionCommon.ExtensionAPI {
   getAPI(context) {
@@ -43,7 +11,7 @@ var windowEvent = class extends ExtensionCommon.ExtensionAPI {
     return {
       // Again, this key must have the same name.
       windowEvent: {
-        setCloseType: function (type) {
+        setCloseType: async function (type) {
           windowListener.setCloseType(type);
         },
 
@@ -136,7 +104,6 @@ var windowListener = new (class extends ExtensionCommon.EventEmitter {
               windowListener.onCloseButton,
               true
             );
-            windowListener.hijackTitlebarCloseButton(window);
           }
         },
       });
@@ -171,58 +138,4 @@ var windowListener = new (class extends ExtensionCommon.EventEmitter {
     if (event) event.preventDefault();
     return true;
   }
-
-  hijackTitlebarCloseButton(window) {
-    if (
-      windowListener.replaceCommand(window, "titlebar-close", function () {
-        return windowListener.onCloseButton(null);
-      })
-    ) {
-      console.log("replaced command= " + "titlebar-close");
-    }
-  }
-
-  replaceCommand(window, eltId, gotHidden) {
-    let elt = window.document.getElementById(eltId);
-    if (!elt) {
-      console.log("Element '" + eltId + "' not found. Command not replaced.");
-      return false;
-    }
-
-    let prevent = null;
-    if (elt.command) {
-      prevent = {
-        event: "click",
-        func: function (e) {
-          e.preventDefault();
-        },
-      };
-    } else if (elt.getAttribute("oncommand")) {
-      prevent = {
-        event: "command",
-        func: function (e) {
-          e.stopPropagation();
-        },
-      };
-    } else {
-      console.warn("Could not replace oncommand on " + eltId);
-      return false;
-    }
-
-    let callback = function (event) {
-      if (event.target.id === eltId) {
-        console.debug(prevent.event + " on " + eltId);
-        if (gotHidden()) prevent.func(event);
-      }
-    };
-
-    /* We put listeners on the "titlebar" parent node, because:
-     - we can hardly short-circuit command/oncommand (probably because they are
-       registered first)
-     - we'd have otherwise to alter "oncommand"/"command" attribute and use
-       Function(), which do not pass review nowadays. */
-    elt.parentNode.addEventListener(prevent.event, callback, true);
-
-    return true;
-  }
 })();
diff --git a/webext/schema_folderchange.json b/webext/schema_folderchange.json
index 449fb6d..046041c 100644
--- a/webext/schema_folderchange.json
+++ b/webext/schema_folderchange.json
@@ -6,6 +6,7 @@
         "name": "setVersion",
         "type": "function",
         "description": "Set the TB version.",
+        "async": true,
         "parameters": [
           {
             "type": "integer",
@@ -19,6 +20,7 @@
         "name": "setCountType",
         "type": "function",
         "description": "Set the count type.",
+        "async": true,
         "parameters": [
           {
             "type": "integer",
@@ -32,6 +34,7 @@
         "name": "setFilters",
         "type": "function",
         "description": "Set the account filters.",
+        "async": true,
         "parameters": [
           {
             "name": "filters",
diff --git a/webext/schema_windowEvent.json b/webext/schema_windowEvent.json
index 668f549..a8a4c47 100644
--- a/webext/schema_windowEvent.json
+++ b/webext/schema_windowEvent.json
@@ -6,6 +6,7 @@
         "name": "setCloseType",
         "type": "function",
         "description": "Set the close type.",
+        "async": true,
         "parameters": [
           {
             "type": "integer",