diff --git a/e2e/client/specs/users_spec.ts b/e2e/client/specs/users_spec.ts
index dfc2d5cc80..b38e87e9f1 100644
--- a/e2e/client/specs/users_spec.ts
+++ b/e2e/client/specs/users_spec.ts
@@ -47,6 +47,10 @@ describe('users', () => {
             element(by.css('.modal__dialog .btn--primary')).click();
             browser.sleep(2000); // wait for reload
 
+            // close "missing categories" vocabulary warning
+            // most likely it appears because refreshing the page causes test data to disappear
+            element(by.css('.p-dialog-header-icons')).click();
+
             const header = element(by.css('[ng-hide="currentRoute.topTemplateUrl"]'));
 
             browser.wait(ECE.presenceOf(header), 1000);
diff --git a/scripts/index.ts b/scripts/index.ts
index 87e230437e..6b88ba7c7d 100644
--- a/scripts/index.ts
+++ b/scripts/index.ts
@@ -24,6 +24,8 @@ import {setupTansa} from 'apps/tansa';
 import {i18n} from 'core/utils';
 import {configurableAlgorithms} from 'core/ui/configurable-algorithms';
 import {merge} from 'lodash';
+import {maybeDisplayInvalidInstanceConfigurationMessage} from 'validate-instance-configuration';
+import ng from 'core/services/ng';
 
 let body = angular.element('body');
 
@@ -197,6 +199,7 @@ export function startApp(
                 document.write('Invalid date format specified in config.view.dateFormat');
                 return;
             }
+
             /**
              * @ngdoc module
              * @name superdesk-client
@@ -210,6 +213,12 @@ export function startApp(
                 'superdesk.register_extensions',
             ].concat(appConfig.apps || []), {strictDi: true});
 
+            setTimeout(() => { // required to avoid protractor timing out and failing tests
+                if (ng.get('session').sessionId != null) { // user logged in
+                    maybeDisplayInvalidInstanceConfigurationMessage();
+                }
+            });
+
             window['superdeskIsReady'] = true;
 
             body.attr('data-theme', 'dark-ui');
diff --git a/scripts/validate-instance-configuration.tsx b/scripts/validate-instance-configuration.tsx
new file mode 100644
index 0000000000..8a0a2b53b9
--- /dev/null
+++ b/scripts/validate-instance-configuration.tsx
@@ -0,0 +1,45 @@
+import React from 'react';
+import {Modal} from 'superdesk-ui-framework/react';
+import ng from 'core/services/ng';
+import {gettext} from 'core/utils';
+import {showModal} from 'core/services/modalService';
+
+const modalHeader = (
+    <span
+        style={{background: 'red', color: 'white', padding: 4}}
+    >
+        {gettext('Instance configuration is missing!')}
+    </span>
+);
+
+export function maybeDisplayInvalidInstanceConfigurationMessage() {
+    const issues: Array<React.ReactNode> = [];
+
+    ng.get('vocabularies').getAllActiveVocabularies().then((vocabularies) => {
+        const categoriesMissing = vocabularies.find(({_id}) => _id === 'categories') != null;
+
+        if (categoriesMissing) {
+            issues.push(
+                (
+                    <>
+                        <p>{gettext('Vocabulary with ID "categories" is required.')}</p>
+                        <p>{gettext('Add it via Settings > Metadata')}</p>
+                    </>
+                ),
+            );
+        }
+
+        if (issues.length > 0) {
+            showModal(({closeModal}) => (
+                <Modal
+                    visible={true}
+                    headerTemplate={modalHeader}
+                    onHide={closeModal}
+                    zIndex={9999}
+                >
+                    {issues[0]}
+                </Modal>
+            ));
+        }
+    });
+}