diff --git a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
index 090fad7362..3aeea3b431 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
@@ -75,7 +75,7 @@ export class GrGroupAuditLog extends ListViewMixin(
     }
 
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     return this.restApiService
diff --git a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log_test.js b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log_test.js
index 25fd85407c..268112ed40 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log_test.js
@@ -18,6 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-group-audit-log.js';
 import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-group-audit-log');
 
@@ -84,7 +85,7 @@ suite('gr-group-audit-log tests', () => {
         errFn(response);
       });
 
-      element.addEventListener('page-error', e => {
+      addListenerForTest(document, 'page-error', e => {
         assert.deepEqual(e.detail.response, response);
         done();
       });
diff --git a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
index 4c546175a3..888647fed3 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
@@ -139,7 +139,7 @@ export class GrGroupMembers extends GestureEventListeners(
     const promises: Promise<void>[] = [];
 
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     return this.restApiService
diff --git a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members_test.js b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members_test.js
index c09ac1ea97..654d24ac04 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members_test.js
@@ -18,7 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-group-members.js';
 import {dom, flush} from '@polymer/polymer/lib/legacy/polymer.dom.js';
-import {stubBaseUrl, stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubBaseUrl, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-group-members');
 
@@ -352,7 +352,7 @@ suite('gr-group-members tests', () => {
         .callsFake((group, errFn) => {
           errFn(response);
         });
-    element.addEventListener('page-error', e => {
+    addListenerForTest(document, 'page-error', e => {
       assert.deepEqual(e.detail.response, response);
       done();
     });
diff --git a/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts b/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
index 3b0577e1d3..cee803ccc1 100644
--- a/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
@@ -148,7 +148,7 @@ export class GrGroup extends GestureEventListeners(
     const promises: Promise<unknown>[] = [];
 
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     return this.restApiService
diff --git a/polygerrit-ui/app/elements/admin/gr-group/gr-group_test.js b/polygerrit-ui/app/elements/admin/gr-group/gr-group_test.js
index 4a80946c00..4c09e307ec 100644
--- a/polygerrit-ui/app/elements/admin/gr-group/gr-group_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-group/gr-group_test.js
@@ -18,6 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-group.js';
 import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-group');
 
@@ -216,7 +217,7 @@ suite('gr-group tests', () => {
       errFn(response);
     });
 
-    element.addEventListener('page-error', e => {
+    addListenerForTest(document, 'page-error', e => {
       assert.deepEqual(e.detail.response, response);
       done();
     });
diff --git a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
index 2d1d1ce67e..ceb08b64b7 100644
--- a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
@@ -95,7 +95,7 @@ export class GrPluginList extends ListViewMixin(
 
   _getPlugins(filter: string, pluginsPerPage: number, offset?: number) {
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
     return this.restApiService
       .getPlugins(filter, pluginsPerPage, offset, errFn)
diff --git a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list_test.js b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list_test.js
index 82e0f8c6f1..a9281e492c 100644
--- a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list_test.js
@@ -18,7 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-plugin-list.js';
 import 'lodash/lodash.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-plugin-list');
 
@@ -155,7 +155,7 @@ suite('gr-plugin-list tests', () => {
             errFn(response);
           });
 
-      element.addEventListener('page-error', e => {
+      addListenerForTest(document, 'page-error', e => {
         assert.deepEqual(e.detail.response, response);
         done();
       });
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts
index b46a9059cd..19fac2f137 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.ts
@@ -151,7 +151,7 @@ export class GrRepoAccess extends GestureEventListeners(
 
   _reload(repo: RepoName) {
     const errFn = (response?: Response | null) => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     this._editing = false;
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access_test.js b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access_test.js
index 1f73b4c78e..a4e019eded 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access_test.js
@@ -20,7 +20,7 @@ import './gr-repo-access.js';
 import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation.js';
 import {toSortedPermissionsArray} from '../../../utils/access-util.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-repo-access');
 
@@ -242,7 +242,7 @@ suite('gr-repo-access tests', () => {
       errFn(response);
     });
 
-    element.addEventListener('page-error', e => {
+    addListenerForTest(document, 'page-error', e => {
       assert.deepEqual(e.detail.response, response);
       done();
     });
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
index 59a203447a..9bc0466ffd 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
@@ -106,7 +106,7 @@ export class GrRepoCommands extends GestureEventListeners(
       // Do not process the error, if the component is not attached to the DOM
       // anymore, which at least in tests can happen.
       if (!this.isConnected) return;
-      firePageError(this, response);
+      firePageError(response);
     };
 
     this.restApiService.getProjectConfig(this.repo, errFn).then(config => {
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands_test.js b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands_test.js
index b01b654830..893efe556c 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands_test.js
@@ -18,7 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-repo-commands.js';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-repo-commands');
 
@@ -121,7 +121,7 @@ suite('gr-repo-commands tests', () => {
       stubRestApi('getProjectConfig').callsFake((repo, errFn) => {
         errFn(response);
       });
-      element.addEventListener('page-error', e => {
+      addListenerForTest(document, 'page-error', e => {
         assert.deepEqual(e.detail.response, response);
         done();
       });
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts b/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts
index 2f4bbec4db..b30d1f4462 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards.ts
@@ -59,7 +59,7 @@ export class GrRepoDashboards extends GestureEventListeners(
     }
 
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     return this.restApiService
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards_test.js b/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards_test.js
index b84b6b4d8f..829611dfa5 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-repo-dashboards/gr-repo-dashboards_test.js
@@ -18,7 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-repo-dashboards.js';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-repo-dashboards');
 
@@ -128,7 +128,7 @@ suite('gr-repo-dashboards tests', () => {
         errFn(response);
       });
 
-      element.addEventListener('page-error', e => {
+      addListenerForTest(document, 'page-error', e => {
         assert.deepEqual(e.detail.response, response);
         done();
       });
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts b/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts
index 5a05f04633..5325dc7d5c 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list.ts
@@ -181,7 +181,7 @@ export class GrRepoDetailList extends ListViewMixin(
     this._items = [];
     flush();
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     if (detailType === RepoDetailView.BRANCHES) {
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list_test.js b/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list_test.js
index ed8b762dbd..990ea4b068 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-repo-detail-list/gr-repo-detail-list_test.js
@@ -20,7 +20,7 @@ import './gr-repo-detail-list.js';
 import 'lodash/lodash.js';
 import {page} from '../../../utils/page-wrapper-utils.js';
 import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-repo-detail-list');
 
@@ -293,7 +293,7 @@ suite('gr-repo-detail-list', () => {
               errFn(response);
             });
 
-        element.addEventListener('page-error', e => {
+        addListenerForTest(document, 'page-error', e => {
           assert.deepEqual(e.detail.response, response);
           done();
         });
@@ -488,7 +488,7 @@ suite('gr-repo-detail-list', () => {
               errFn(response);
             });
 
-        element.addEventListener('page-error', e => {
+        addListenerForTest(document, 'page-error', e => {
           assert.deepEqual(e.detail.response, response);
           done();
         });
diff --git a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
index ec511c8f26..5ddafdbdfa 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
@@ -171,7 +171,7 @@ export class GrRepo extends GestureEventListeners(
     const promises = [];
 
     const errFn: ErrorCallback = response => {
-      firePageError(this, response);
+      firePageError(response);
     };
 
     promises.push(
diff --git a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo_test.js b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo_test.js
index e2b26df459..8ce6f646f3 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo_test.js
+++ b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo_test.js
@@ -18,7 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-repo.js';
 import {PolymerElement} from '@polymer/polymer/polymer-element.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-repo');
 
@@ -235,7 +235,7 @@ suite('gr-repo tests', () => {
     stubRestApi('getProjectConfig').callsFake((repo, errFn) => {
       errFn(response);
     });
-    element.addEventListener('page-error', e => {
+    addListenerForTest(document, 'page-error', e => {
       assert.deepEqual(e.detail.response, response);
       done();
     });
diff --git a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
index 078ab03f72..7008b482f2 100644
--- a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
@@ -172,7 +172,7 @@ export class GrDashboardView extends GestureEventListeners(
     dashboard: DashboardId
   ): Promise<UserDashboard | undefined> {
     const errFn = (response?: Response | null) => {
-      firePageError(this, response);
+      firePageError(response);
     };
     return this.restApiService
       .getDashboard(project, dashboard, errFn)
diff --git a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view_test.js b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view_test.js
index 4a4e4ab8e5..47f885bd3e 100644
--- a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view_test.js
+++ b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view_test.js
@@ -23,7 +23,7 @@ import {GerritView} from '../../../services/router/router-model.js';
 import {changeIsOpen} from '../../../utils/change-util.js';
 import {ChangeStatus} from '../../../constants/constants.js';
 import {createAccountWithId} from '../../../test/test-data-generators.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-dashboard-view');
 
@@ -377,7 +377,7 @@ suite('gr-dashboard-view tests', () => {
         async (project, dashboard, errFn) => {
           errFn(response);
         });
-    element.addEventListener('page-error', e => {
+    addListenerForTest(document, 'page-error', e => {
       assert.strictEqual(e.detail.response, response);
       paramsChangedPromise.then(done);
     });
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
index 5de6db44dc..1e3dfffccc 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
@@ -1855,7 +1855,7 @@ export class GrChangeView extends KeyboardShortcutMixin(
   }
 
   _handleGetChangeDetailError(response?: Response | null) {
-    firePageError(this, response);
+    firePageError(response);
   }
 
   _getLoggedIn() {
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
index e0b40b1ade..582d96b9eb 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
@@ -65,6 +65,7 @@ import {
 } from '../../gr-app-types';
 import {LocationChangeEventDetail} from '../../../types/events';
 import {GerritView, updateState} from '../../../services/router/router-model';
+import {firePageError} from '../../../utils/event-util';
 
 const RoutePattern = {
   ROOT: '/',
@@ -1777,9 +1778,7 @@ export class GrRouter extends GestureEventListeners(
     // Note: the app's 404 display is tightly-coupled with catching 404
     // network responses, so we simulate a 404 response status to display it.
     // TODO: Decouple the gr-app error view from network responses.
-    this._appElement().dispatchEvent(
-      new CustomEvent('page-error', {detail: {response: {status: 404}}})
-    );
+    firePageError(new Response('', {status: 404}));
   }
 }
 
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js b/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js
index 16d6370baf..ec122ec7b6 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router_test.js
@@ -22,6 +22,7 @@ import {GerritNav} from '../gr-navigation/gr-navigation.js';
 import {stubBaseUrl} from '../../../test/test-utils.js';
 import {_testOnly_RoutePattern} from './gr-router.js';
 import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-router');
 
@@ -664,13 +665,11 @@ suite('gr-router tests', () => {
     });
 
     test('_handleDefaultRoute on first load', () => {
-      const appElementStub = {dispatchEvent: sinon.stub()};
-      element._appElement = () => appElementStub;
+      const spy = sinon.spy();
+      addListenerForTest(document, 'page-error', spy);
       element._handleDefaultRoute();
-      assert.isTrue(appElementStub.dispatchEvent.calledOnce);
-      assert.equal(
-          appElementStub.dispatchEvent.lastCall.args[0].detail.response.status,
-          404);
+      assert.isTrue(spy.calledOnce);
+      assert.equal(spy.lastCall.args[0].detail.response.status, 404);
     });
 
     test('_handleDefaultRoute after internal navigation', () => {
@@ -684,8 +683,6 @@ suite('gr-router tests', () => {
       sinon.stub(page, 'base');
       element._startRouter();
 
-      const appElementStub = {dispatchEvent: sinon.stub()};
-      element._appElement = () => appElementStub;
       element._handleDefaultRoute();
 
       onExit('', () => {}); // we left page;
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
index afc15dd1ad..7610e5e6c8 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.ts
@@ -609,7 +609,7 @@ export class GrDiffHost extends GestureEventListeners(
       return;
     }
 
-    firePageError(this, response);
+    firePageError(response);
   }
 
   /**
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
index 99e639105c..dd2e30748a 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.js
@@ -25,7 +25,7 @@ import {Side, CommentSide} from '../../../constants/constants.js';
 import {createChange} from '../../../test/test-data-generators.js';
 import {FILE} from '../gr-diff/gr-diff-line.js';
 import {CoverageType} from '../../../types/types.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 import {createDefaultDiffPrefs} from '../../../constants/constants.js';
 
 const basicFixture = fixtureFromElement('gr-diff-host');
@@ -296,13 +296,9 @@ suite('gr-diff-host tests', () => {
 
       setup(() => {
         serverErrorStub = sinon.stub();
-        document.addEventListener('server-error', serverErrorStub);
+        addListenerForTest(document, 'server-error', serverErrorStub);
         pageErrorStub = sinon.stub();
-        element.addEventListener('page-error', pageErrorStub);
-      });
-
-      teardown(() => {
-        document.removeEventListener('server-error', serverErrorStub);
+        addListenerForTest(document, 'page-error', pageErrorStub);
       });
 
       test('page error on HTTP-409', () => {
@@ -313,7 +309,10 @@ suite('gr-diff-host tests', () => {
       });
 
       test('server error on non-HTTP-409', () => {
-        element._handleGetDiffError({status: 500});
+        element._handleGetDiffError({
+          status: 500,
+          text: () => Promise.resolve(''),
+        });
         assert.isFalse(serverErrorStub.called);
         assert.isTrue(pageErrorStub.calledOnce);
         assert.isNotOk(element._errorMessage);
diff --git a/polygerrit-ui/app/elements/gr-app-element.ts b/polygerrit-ui/app/elements/gr-app-element.ts
index 07e9aab272..15e89230b3 100644
--- a/polygerrit-ui/app/elements/gr-app-element.ts
+++ b/polygerrit-ui/app/elements/gr-app-element.ts
@@ -210,7 +210,7 @@ export class GrAppElement extends KeyboardShortcutMixin(
   created() {
     super.created();
     this._bindKeyboardShortcuts();
-    this.addEventListener(EventType.PAGE_ERROR, e => {
+    document.addEventListener(EventType.PAGE_ERROR, e => {
       this._handlePageError(e);
     });
     this.addEventListener(EventType.TITLE_CHANGE, e => {
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context_test.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context_test.js
index e764bf85d4..34c976a3e9 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context_test.js
@@ -19,6 +19,7 @@ import '../../../test/common-test-setup-karma.js';
 import './gr-js-api-interface.js';
 import {GrPluginActionContext} from './gr-plugin-action-context.js';
 import {_testOnly_initGerritPluginApi} from './gr-gerrit.js';
+import {addListenerForTest} from '../../../test/test-utils.js';
 
 const pluginApi = _testOnly_initGerritPluginApi();
 
@@ -137,7 +138,7 @@ suite('gr-plugin-action-context tests', () => {
       send: sendStub,
     });
     const errorStub = sinon.stub();
-    document.addEventListener('show-alert', errorStub);
+    addListenerForTest(document, 'show-alert', errorStub);
     instance.call();
     await flush();
     assert.isTrue(errorStub.calledOnce);
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-loader_test.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-loader_test.js
index 66248c63cb..19762e0487 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-loader_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-loader_test.js
@@ -22,7 +22,7 @@ import {_testOnly_resetPluginLoader} from './gr-plugin-loader.js';
 import {resetPlugins, stubBaseUrl} from '../../../test/test-utils.js';
 import {_testOnly_flushPreinstalls} from './gr-gerrit.js';
 import {_testOnly_initGerritPluginApi} from './gr-gerrit.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import {addListenerForTest, stubRestApi} from '../../../test/test-utils.js';
 
 const basicFixture = fixtureFromElement('gr-js-api-interface');
 
@@ -149,7 +149,7 @@ suite('gr-plugin-loader tests', () => {
     ];
 
     const alertStub = sinon.stub();
-    document.addEventListener('show-alert', alertStub);
+    addListenerForTest(document, 'show-alert', alertStub);
 
     sinon.stub(pluginLoader, '_loadJsPlugin').callsFake( url => {
       pluginApi.install(() => {
@@ -177,7 +177,7 @@ suite('gr-plugin-loader tests', () => {
     ];
 
     const alertStub = sinon.stub();
-    document.addEventListener('show-alert', alertStub);
+    addListenerForTest(document, 'show-alert', alertStub);
 
     sinon.stub(pluginLoader, '_loadJsPlugin').callsFake( url => {
       pluginApi.install(() => {
@@ -210,7 +210,7 @@ suite('gr-plugin-loader tests', () => {
     ];
 
     const alertStub = sinon.stub();
-    document.addEventListener('show-alert', alertStub);
+    addListenerForTest(document, 'show-alert', alertStub);
 
     sinon.stub(pluginLoader, '_loadJsPlugin').callsFake( url => {
       pluginApi.install(() => {
@@ -236,7 +236,7 @@ suite('gr-plugin-loader tests', () => {
     ];
 
     const alertStub = sinon.stub();
-    document.addEventListener('show-alert', alertStub);
+    addListenerForTest(document, 'show-alert', alertStub);
 
     sinon.stub(pluginLoader, '_loadJsPlugin').callsFake( url => {
       pluginApi.install(() => {
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
index 61e9ff275d..355691f5d9 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.ts
@@ -16,8 +16,6 @@
  */
 /* NB: Order is important, because of namespaced classes. */
 
-import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
-import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
 import {PolymerElement} from '@polymer/polymer/polymer-element';
 import {GrEtagDecorator} from './gr-etag-decorator';
 import {
@@ -41,7 +39,7 @@ import {
   listChangesOptionsToHex,
 } from '../../../utils/change-util';
 import {assertNever, hasOwnProperty} from '../../../utils/common-util';
-import {customElement, property} from '@polymer/decorators';
+import {customElement} from '@polymer/decorators';
 import {AuthRequestInit, AuthService} from '../../../services/gr-auth/gr-auth';
 import {
   AccountCapabilityInfo,
@@ -297,22 +295,16 @@ declare global {
 }
 
 @customElement('gr-rest-api-interface')
-export class GrRestApiInterface
-  extends GestureEventListeners(LegacyElementMixin(PolymerElement))
+export class GrRestApiInterface extends PolymerElement
   implements RestApiService {
-  @property({type: Object})
   readonly _cache = siteBasedCache; // Shared across instances.
 
-  @property({type: Object})
   readonly _sharedFetchPromises = fetchPromisesCache; // Shared across instances.
 
-  @property({type: Object})
   readonly _pendingRequests = pendingRequest; // Shared across instances.
 
-  @property({type: Object})
   readonly _etags = grEtagDecorator; // Shared across instances.
 
-  @property({type: Object})
   readonly _projectLookup = projectLookup; // Shared across instances.
 
   // The value is set in created, before any other actions
@@ -3067,8 +3059,7 @@ export class GrRestApiInterface
       return Promise.resolve(project);
     }
 
-    const onError = (response?: Response | null) =>
-      firePageError(this, response);
+    const onError = (response?: Response | null) => firePageError(response);
 
     return this.getChange(changeNum, onError).then(change => {
       if (!change || !change.project) {
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.js b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.js
index 4c80db56c2..6db2bff325 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.js
@@ -16,8 +16,7 @@
  */
 
 import '../../../test/common-test-setup-karma.js';
-import './gr-rest-api-interface.js';
-import {mockPromise} from '../../../test/test-utils.js';
+import {addListenerForTest, mockPromise} from '../../../test/test-utils.js';
 import {GrReviewerUpdatesParser} from './gr-reviewer-updates-parser.js';
 import {ListChangesOption} from '../../../utils/change-util.js';
 import {appContext} from '../../../services/app-context.js';
@@ -28,8 +27,7 @@ import {
   readResponsePayload,
 } from './gr-rest-apis/gr-rest-api-helper.js';
 import {JSON_PREFIX} from './gr-rest-apis/gr-rest-api-helper.js';
-
-const basicFixture = fixtureFromElement('gr-rest-api-interface');
+import {GrRestApiInterface} from './gr-rest-api-interface.js';
 
 suite('gr-rest-api-interface tests', () => {
   let element;
@@ -53,7 +51,7 @@ suite('gr-rest-api-interface tests', () => {
     // fake auth
     sinon.stub(appContext.authService, 'authCheck')
         .returns(Promise.resolve(true));
-    element = basicFixture.instantiate();
+    element = new GrRestApiInterface();
     element._projectLookup = {};
   });
 
@@ -267,7 +265,7 @@ suite('gr-rest-api-interface tests', () => {
     const getResponseObjectStub = sinon.stub(element, 'getResponseObject');
     window.fetch.returns(Promise.resolve({ok: false}));
     const serverErrorEventPromise = new Promise(resolve => {
-      document.addEventListener('server-error', resolve);
+      addListenerForTest(document, 'server-error', resolve);
     });
 
     return Promise.all([element._restApiHelper.fetchJSON({}).then(response => {
@@ -1253,7 +1251,7 @@ suite('gr-rest-api-interface tests', () => {
   test('getFileContent suppresses 404s', () => {
     const res = {status: 404};
     const spy = sinon.spy();
-    document.addEventListener('server-error', spy);
+    addListenerForTest(document, 'server-error', spy);
     sinon.stub(appContext.authService, 'fetch').returns(Promise.resolve(res));
     sinon.stub(element, '_changeBaseURL').returns(Promise.resolve(''));
     return element.getFileContent('1', 'tst/path', '1')
@@ -1306,7 +1304,7 @@ suite('gr-rest-api-interface tests', () => {
   test('_logCall only reports requests with anonymized URLss', () => {
     sinon.stub(Date, 'now').returns(200);
     const handler = sinon.stub();
-    document.addEventListener('gr-rpc-log', handler);
+    addListenerForTest(document, 'gr-rpc-log', handler);
 
     element._restApiHelper._logCall({url: 'url'}, 100, 200);
     assert.isFalse(handler.called);
@@ -1320,14 +1318,13 @@ suite('gr-rest-api-interface tests', () => {
   test('ported comment errors do not trigger error dialog', () => {
     const change = createChange();
     const handler = sinon.stub();
-    document.addEventListener('server-error', handler);
+    addListenerForTest(document, 'server-error', handler);
     sinon.stub(element._restApiHelper, 'fetchJSON').returns(Promise.resolve({
       ok: false}));
 
     element.getPortedComments(change._number, CURRENT);
 
     assert.isFalse(handler.called);
-    document.removeEventListener('server-error', handler);
   });
 
   test('ported drafts are not requested user is not logged in', () => {
diff --git a/polygerrit-ui/app/types/events.ts b/polygerrit-ui/app/types/events.ts
index 2398a6689d..48138287f4 100644
--- a/polygerrit-ui/app/types/events.ts
+++ b/polygerrit-ui/app/types/events.ts
@@ -40,7 +40,7 @@ export interface PageErrorEventDetail {
 export type PageErrorEvent = CustomEvent<PageErrorEventDetail>;
 
 declare global {
-  interface HTMLElementEventMap {
+  interface DocumentEventMap {
     'page-error': PageErrorEvent;
   }
 }
diff --git a/polygerrit-ui/app/utils/event-util.ts b/polygerrit-ui/app/utils/event-util.ts
index 5c7cd6d053..9938e11901 100644
--- a/polygerrit-ui/app/utils/event-util.ts
+++ b/polygerrit-ui/app/utils/event-util.ts
@@ -46,8 +46,8 @@ export function fireAlert(target: EventTarget, message: string) {
   );
 }
 
-export function firePageError(target: EventTarget, response?: Response | null) {
-  target.dispatchEvent(
+export function firePageError(response?: Response | null) {
+  document.dispatchEvent(
     new CustomEvent(EventType.PAGE_ERROR, {
       detail: {response},
       composed: true,