diff --git a/js/misc/dbusErrors.js b/js/misc/dbusErrors.js
index 5e4d62e2c..f59add314 100644
--- a/js/misc/dbusErrors.js
+++ b/js/misc/dbusErrors.js
@@ -1,4 +1,3 @@
-/* eslint-disable no-unused-vars */
 import GLib from 'gi://GLib';
 import Gio from 'gi://Gio';
 
@@ -27,3 +26,11 @@ function createErrorEnum(errorNames) {
     }
     return obj;
 }
+
+const modalDialogErrorNames = [
+    'UnknownType',
+    'GrabFailed',
+];
+export const ModalDialogErrors =
+    registerErrorDomain('ModalDialog', modalDialogErrorNames);
+export const ModalDialogError = createErrorEnum(modalDialogErrorNames);
diff --git a/js/ui/endSessionDialog.js b/js/ui/endSessionDialog.js
index d133c38c0..6f5aadd7c 100644
--- a/js/ui/endSessionDialog.js
+++ b/js/ui/endSessionDialog.js
@@ -34,6 +34,8 @@ import * as LoginManager from '../misc/loginManager.js';
 import * as ModalDialog from './modalDialog.js';
 import * as UserWidget from './userWidget.js';
 
+import {ModalDialogErrors, ModalDialogError} from '../misc/dbusErrors.js';
+
 import {loadInterfaceXML} from '../misc/fileUtils.js';
 
 const _ITEM_ICON_SIZE = 64;
@@ -739,8 +741,8 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
         this._sessionSection.list.destroy_all_children();
 
         if (!(this._type in DialogContent)) {
-            invocation.return_dbus_error(
-                'org.gnome.Shell.ModalDialog.TypeError',
+            invocation.return_error_literal(ModalDialogErrors,
+                ModalDialogError.UNKNOWN_TYPE,
                 'Unknown dialog type requested');
             return;
         }
@@ -773,8 +775,8 @@ class EndSessionDialog extends ModalDialog.ModalDialog {
         this._updateButtons();
 
         if (!this.open(timestamp)) {
-            invocation.return_dbus_error(
-                'org.gnome.Shell.ModalDialog.GrabError',
+            invocation.return_error_literal(
+                ModalDialogError.GRAB_FAILED,
                 'Cannot grab pointer and keyboard');
             return;
         }