diff --git a/js/gdm/loginDialog.js b/js/gdm/loginDialog.js
index b3afa343a..810920617 100644
--- a/js/gdm/loginDialog.js
+++ b/js/gdm/loginDialog.js
@@ -750,12 +750,12 @@ function LoginDialog() {
     return _loginDialog;
 }
 
-LoginDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const LoginDialog = new Lang.Class({
+    Name: 'LoginDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function() {
-        ModalDialog.ModalDialog.prototype._init.call(this, { shellReactive: true,
-                                                             styleClass: 'login-dialog' });
+        this.parent({ shellReactive: true, styleClass: 'login-dialog' });
         this.connect('destroy',
                      Lang.bind(this, this._onDestroy));
         this.connect('opened',
@@ -1399,8 +1399,8 @@ LoginDialog.prototype = {
     },
 
     close: function() {
-        ModalDialog.ModalDialog.prototype.close.call(this);
+        this.parent();
 
         Main.ctrlAltTabManager.removeGroup(this._group);
     }
-};
+});
diff --git a/js/ui/endSessionDialog.js b/js/ui/endSessionDialog.js
index 4650097a3..947524a76 100644
--- a/js/ui/endSessionDialog.js
+++ b/js/ui/endSessionDialog.js
@@ -230,27 +230,19 @@ function _setLabelText(label, text) {
     }
 }
 
-function EndSessionDialog() {
-    if (_endSessionDialog == null) {
-        this._init();
-        _endSessionDialog = this;
-    }
-
-    return _endSessionDialog;
-}
-
 function init() {
     // This always returns the same singleton object
     // By instantiating it initially, we register the
     // bus object, etc.
-    let dialog = new EndSessionDialog();
+    _endSessionDialog = new EndSessionDialog();
 }
 
-EndSessionDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const EndSessionDialog = new Lang.Class({
+    Name: 'EndSessionDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function() {
-        ModalDialog.ModalDialog.prototype._init.call(this, { styleClass: 'end-session-dialog' });
+        this.parent({ styleClass: 'end-session-dialog' });
 
         this._user = AccountsService.UserManager.get_default().get_user(GLib.get_user_name());
 
@@ -441,7 +433,7 @@ EndSessionDialog.prototype = {
     },
 
     close: function() {
-        ModalDialog.ModalDialog.prototype.close.call(this);
+        this.parent();
         this._dbusImpl.emit_signal('Closed', null);
     },
 
@@ -543,4 +535,4 @@ EndSessionDialog.prototype = {
                                         this.disconnect(signalId);
                                     }));
     }
-};
+});
diff --git a/js/ui/extensionSystem.js b/js/ui/extensionSystem.js
index a1fdbdefe..a0302fe02 100644
--- a/js/ui/extensionSystem.js
+++ b/js/ui/extensionSystem.js
@@ -502,15 +502,12 @@ function loadExtensions() {
     _loadExtensionsIn(userExtensionsDir, ExtensionType.PER_USER);
 }
 
-function InstallExtensionDialog(uuid, version_tag, name) {
-    this._init(uuid, version_tag, name);
-}
-
-InstallExtensionDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const InstallExtensionDialog = new Lang.Class({
+    Name: 'InstallExtensionDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function(uuid, version_tag, name) {
-        ModalDialog.ModalDialog.prototype._init.call(this, { styleClass: 'extension-dialog' });
+        this.parent({ styleClass: 'extension-dialog' });
 
         this._uuid = uuid;
         this._version_tag = version_tag;
@@ -570,4 +567,4 @@ InstallExtensionDialog.prototype = {
 
         this.close(global.get_current_time());
     }
-};
+});
diff --git a/js/ui/modalDialog.js b/js/ui/modalDialog.js
index c2f3b3982..a6479595e 100644
--- a/js/ui/modalDialog.js
+++ b/js/ui/modalDialog.js
@@ -29,11 +29,9 @@ const State = {
     FADED_OUT: 4
 };
 
-function ModalDialog() {
-    this._init();
-}
+const ModalDialog = new Lang.Class({
+    Name: 'ModalDialog',
 
-ModalDialog.prototype = {
     _init: function(params) {
         params = Params.parse(params, { shellReactive: false,
                                         styleClass: null });
@@ -303,5 +301,5 @@ ModalDialog.prototype = {
                                })
                          });
     }
-};
+});
 Signals.addSignalMethods(ModalDialog.prototype);
diff --git a/js/ui/networkAgent.js b/js/ui/networkAgent.js
index dbb3ed762..276f1403c 100644
--- a/js/ui/networkAgent.js
+++ b/js/ui/networkAgent.js
@@ -32,15 +32,12 @@ const ModalDialog = imports.ui.modalDialog;
 const PopupMenu = imports.ui.popupMenu;
 const ShellEntry = imports.ui.shellEntry;
 
-function NetworkSecretDialog() {
-    this._init.apply(this, arguments);
-}
-
-NetworkSecretDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const NetworkSecretDialog = new Lang.Class({
+    Name: 'NetworkSecretDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function(agent, requestId, connection, settingName, hints) {
-        ModalDialog.ModalDialog.prototype._init.call(this, { styleClass: 'polkit-dialog' });
+        this.parent({ styleClass: 'polkit-dialog' });
 
         this._agent = agent;
         this._requestId = requestId;
@@ -358,7 +355,7 @@ NetworkSecretDialog.prototype = {
 
         return content;
     }
-};
+});
 
 function NetworkAgent() {
     this._init.apply(this, arguments);
diff --git a/js/ui/polkitAuthenticationAgent.js b/js/ui/polkitAuthenticationAgent.js
index 6f0103975..7fe03105b 100644
--- a/js/ui/polkitAuthenticationAgent.js
+++ b/js/ui/polkitAuthenticationAgent.js
@@ -36,15 +36,12 @@ const PolkitAgent = imports.gi.PolkitAgent;
 const ModalDialog = imports.ui.modalDialog;
 const ShellEntry = imports.ui.shellEntry;
 
-function AuthenticationDialog(actionId, message, cookie, userNames) {
-    this._init(actionId, message, cookie, userNames);
-}
-
-AuthenticationDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const AuthenticationDialog = new Lang.Class({
+    Name: 'AuthenticationDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function(actionId, message, cookie, userNames) {
-        ModalDialog.ModalDialog.prototype._init.call(this, { styleClass: 'polkit-dialog' });
+        this.parent({ styleClass: 'polkit-dialog' });
 
         this.actionId = actionId;
         this.message = message;
@@ -335,8 +332,7 @@ AuthenticationDialog.prototype = {
         this.close(global.get_current_time());
         this._emitDone(false, true);
     },
-
-};
+});
 Signals.addSignalMethods(AuthenticationDialog.prototype);
 
 function AuthenticationAgent() {
diff --git a/js/ui/shellMountOperation.js b/js/ui/shellMountOperation.js
index 439be580b..ba5f45e41 100644
--- a/js/ui/shellMountOperation.js
+++ b/js/ui/shellMountOperation.js
@@ -192,15 +192,12 @@ ShellMountOperation.prototype = {
     },
 }
 
-function ShellMountQuestionDialog(icon) {
-    this._init(icon);
-}
-
-ShellMountQuestionDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const ShellMountQuestionDialog = new Lang.Class({
+    Name: 'ShellMountQuestionDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function(icon) {
-        ModalDialog.ModalDialog.prototype._init.call(this, { styleClass: 'mount-question-dialog' });
+        this.parent({ styleClass: 'mount-question-dialog' });
 
         let mainContentLayout = new St.BoxLayout();
         this.contentLayout.add(mainContentLayout, { x_fill: true,
@@ -236,7 +233,7 @@ ShellMountQuestionDialog.prototype = {
         _setLabelsForMessage(this, message);
         _setButtonsForChoices(this, choices);
     }
-}
+});
 Signals.addSignalMethods(ShellMountQuestionDialog.prototype);
 
 const ShellMountPasswordSource = new Lang.Class({
@@ -298,15 +295,12 @@ const ShellMountPasswordNotification = new Lang.Class({
     }
 });
 
-function ShellProcessesDialog(icon) {
-    this._init(icon);
-}
-
-ShellProcessesDialog.prototype = {
-    __proto__: ModalDialog.ModalDialog.prototype,
+const ShellProcessesDialog = new Lang.Class({
+    Name: 'ShellProcessesDialog',
+    Extends: ModalDialog.ModalDialog,
 
     _init: function(icon) {
-        ModalDialog.ModalDialog.prototype._init.call(this, { styleClass: 'show-processes-dialog' });
+        this.parent({ styleClass: 'show-processes-dialog' });
 
         let mainContentLayout = new St.BoxLayout();
         this.contentLayout.add(mainContentLayout, { x_fill: true,
@@ -392,5 +386,5 @@ ShellProcessesDialog.prototype = {
         _setLabelsForMessage(this, message);
         _setButtonsForChoices(this, choices);
     }
-}
+});
 Signals.addSignalMethods(ShellProcessesDialog.prototype);