diff --git a/src/lib/app.ts b/src/lib/app.ts
index eb6353e257..c4b52aa38a 100644
--- a/src/lib/app.ts
+++ b/src/lib/app.ts
@@ -23,6 +23,23 @@ import ossAuthentication from './middleware/oss-authentication';
 import noAuthentication from './middleware/no-authentication';
 import secureHeaders from './middleware/secure-headers';
 
+function handleCustomAuth({ customAuthHandler, app, config, services }) {
+    const logger = config.getLogger('src/lib/app/customAuthHandler');
+    if (customAuthHandler) {
+        customAuthHandler(app, config, services);
+    } else {
+        app.use(`${config.server.baseUriPath}/api`, async (req, res) => {
+            logger.error(
+                'You have to configure a custom authentication middleware. Read the docs....',
+            );
+            res.status(401).send({
+                error:
+                    'You have to configure a custom authentication middleware. Read the docs....',
+            });
+        });
+    }
+}
+
 export default function getApp(
     config: IUnleashConfig,
     stores: IUnleashStores,
@@ -70,12 +87,22 @@ export default function getApp(
         }
         case IAuthType.ENTERPRISE: {
             app.use(baseUriPath, apiTokenMiddleware(config, services));
-            config.authentication.customAuthHandler(app, config, services);
+            handleCustomAuth({
+                customAuthHandler: config.authentication.customAuthHandler,
+                app,
+                config,
+                services,
+            });
             break;
         }
         case IAuthType.HOSTED: {
             app.use(baseUriPath, apiTokenMiddleware(config, services));
-            config.authentication.customAuthHandler(app, config, services);
+            handleCustomAuth({
+                customAuthHandler: config.authentication.customAuthHandler,
+                app,
+                config,
+                services,
+            });
             break;
         }
         case IAuthType.DEMO: {
@@ -84,7 +111,12 @@ export default function getApp(
         }
         case IAuthType.CUSTOM: {
             app.use(baseUriPath, apiTokenMiddleware(config, services));
-            config.authentication.customAuthHandler(app, config, services);
+            handleCustomAuth({
+                customAuthHandler: config.authentication.customAuthHandler,
+                app,
+                config,
+                services,
+            });
             break;
         }
         case IAuthType.NONE: {
diff --git a/src/lib/create-config.ts b/src/lib/create-config.ts
index e81f23df24..c8e1a58fd5 100644
--- a/src/lib/create-config.ts
+++ b/src/lib/create-config.ts
@@ -98,7 +98,7 @@ const defaultVersionOption: IVersionOption = {
 const defaultAuthentication: IAuthOption = {
     enableApiToken: safeBoolean(process.env.AUTH_ENABLE_API_TOKEN, true),
     type: authTypeFromString(process.env.AUTH_TYPE),
-    customAuthHandler: () => {},
+    customAuthHandler: undefined,
     createAdminUser: true,
 };
 
diff --git a/src/test/e2e/custom-auth.test.ts b/src/test/e2e/custom-auth.test.ts
new file mode 100644
index 0000000000..3e61844163
--- /dev/null
+++ b/src/test/e2e/custom-auth.test.ts
@@ -0,0 +1,32 @@
+import test, { before } from 'ava';
+
+import dbInit from './helpers/database-init';
+import { setupAppWithCustomAuth } from './helpers/test-helper';
+
+let db;
+let stores;
+
+before(async t => {
+    db = await dbInit('custom_auth_serial');
+    stores = db.stores;
+});
+
+test('Using custom auth type without defining custom middleware causes default DENY ALL policy to take effect', async t => {
+    t.plan(1);
+    const request = await setupAppWithCustomAuth(stores, undefined);
+    await request
+        .get('/api/admin/features')
+        .expect(401)
+        .expect(res => {
+            t.is(
+                res.body.error,
+                'You have to configure a custom authentication middleware. Read the docs....',
+            );
+        });
+});
+
+test('If actually configuring a custom middleware should configure the middleware', async t => {
+    t.plan(0);
+    const request = await setupAppWithCustomAuth(stores, () => {});
+    return request.get('/api/admin/features').expect(200);
+});