diff --git a/src/Configuration/StringAccessibleConfigTrait.php b/src/Configuration/StringAccessibleConfigTrait.php
index 8ea77a22..b2b6f0db 100644
--- a/src/Configuration/StringAccessibleConfigTrait.php
+++ b/src/Configuration/StringAccessibleConfigTrait.php
@@ -137,17 +137,16 @@ trait StringAccessibleConfigTrait
         return true;
     }
 
-    /**
-     * @return bool
-     */
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return $this->has($offset);
     }
 
     /**
-     * @return mixed
+     * @param $offset
+     * @return array|bool|float|int|string|null
      */
+    #[\ReturnTypeWillChange]
     public function offsetGet($offset)
     {
         return $this->find($offset);
diff --git a/src/Controller/SystemConfigurationController.php b/src/Controller/SystemConfigurationController.php
index 9251a9d8..f4312904 100644
--- a/src/Controller/SystemConfigurationController.php
+++ b/src/Controller/SystemConfigurationController.php
@@ -125,15 +125,16 @@ final class SystemConfigurationController extends AbstractController
     }
 
     /**
-     * @Route(path="/update/{section}/{single}", name="system_configuration_update", methods={"POST"})
+     * @Route(path="/update/{section}/{single}", defaults={"single": "0"}, name="system_configuration_update", methods={"POST"})
      *
      * @internal do not link directly to this route
      * @param Request $request
      * @param string $section
      * @return \Symfony\Component\HttpFoundation\RedirectResponse|\Symfony\Component\HttpFoundation\Response
      */
-    public function configUpdate(Request $request, string $section, bool $single)
+    public function configUpdate(Request $request, string $section, string $single)
     {
+        $single = (bool) $single;
         $configModel = null;
         $configSettings = $this->getInitializedConfigurations();
 
diff --git a/tests/Controller/SystemConfigurationControllerTest.php b/tests/Controller/SystemConfigurationControllerTest.php
index 7cdf7044..93c2cd33 100644
--- a/tests/Controller/SystemConfigurationControllerTest.php
+++ b/tests/Controller/SystemConfigurationControllerTest.php
@@ -69,19 +69,19 @@ class SystemConfigurationControllerTest extends ControllerBaseTest
     public function getTestDataForms()
     {
         return [
-            ['form[name=system_configuration_form_timesheet]', $this->createUrl('/admin/system-config/update/timesheet/0')],
-            ['form[name=system_configuration_form_quick_entry]', $this->createUrl('/admin/system-config/update/quick_entry/0')],
-            ['form[name=system_configuration_form_lockdown_period]', $this->createUrl('/admin/system-config/update/lockdown_period/0')],
-            ['form[name=system_configuration_form_invoice]', $this->createUrl('/admin/system-config/update/invoice/0')],
-            ['form[name=system_configuration_form_authentication]', $this->createUrl('/admin/system-config/update/authentication/0')],
-            ['form[name=system_configuration_form_rounding]', $this->createUrl('/admin/system-config/update/rounding/0')],
-            ['form[name=system_configuration_form_customer]', $this->createUrl('/admin/system-config/update/customer/0')],
-            ['form[name=system_configuration_form_project]', $this->createUrl('/admin/system-config/update/project/0')],
-            ['form[name=system_configuration_form_activity]', $this->createUrl('/admin/system-config/update/activity/0')],
-            ['form[name=system_configuration_form_user]', $this->createUrl('/admin/system-config/update/user/0')],
-            ['form[name=system_configuration_form_theme]', $this->createUrl('/admin/system-config/update/theme/0')],
-            ['form[name=system_configuration_form_calendar]', $this->createUrl('/admin/system-config/update/calendar/0')],
-            ['form[name=system_configuration_form_branding]', $this->createUrl('/admin/system-config/update/branding/0')],
+            ['form[name=system_configuration_form_timesheet]', $this->createUrl('/admin/system-config/update/timesheet')],
+            ['form[name=system_configuration_form_quick_entry]', $this->createUrl('/admin/system-config/update/quick_entry')],
+            ['form[name=system_configuration_form_lockdown_period]', $this->createUrl('/admin/system-config/update/lockdown_period')],
+            ['form[name=system_configuration_form_invoice]', $this->createUrl('/admin/system-config/update/invoice')],
+            ['form[name=system_configuration_form_authentication]', $this->createUrl('/admin/system-config/update/authentication')],
+            ['form[name=system_configuration_form_rounding]', $this->createUrl('/admin/system-config/update/rounding')],
+            ['form[name=system_configuration_form_customer]', $this->createUrl('/admin/system-config/update/customer')],
+            ['form[name=system_configuration_form_project]', $this->createUrl('/admin/system-config/update/project')],
+            ['form[name=system_configuration_form_activity]', $this->createUrl('/admin/system-config/update/activity')],
+            ['form[name=system_configuration_form_user]', $this->createUrl('/admin/system-config/update/user')],
+            ['form[name=system_configuration_form_theme]', $this->createUrl('/admin/system-config/update/theme')],
+            ['form[name=system_configuration_form_calendar]', $this->createUrl('/admin/system-config/update/calendar')],
+            ['form[name=system_configuration_form_branding]', $this->createUrl('/admin/system-config/update/branding')],
         ];
     }
 
@@ -217,6 +217,29 @@ class SystemConfigurationControllerTest extends ControllerBaseTest
         $this->assertEquals('GBP', $configService->find('defaults.customer.currency'));
     }
 
+    public function testUpdateCustomerConfigWithSingleParam()
+    {
+        $client = $this->getClientForAuthenticatedUser(User::ROLE_SUPER_ADMIN);
+        $this->assertAccessIsGranted($client, '/admin/system-config/edit/customer');
+
+        $form = $client->getCrawler()->filter('form[name=system_configuration_form_customer]')->form();
+        self::assertStringEndsWith('/admin/system-config/update/customer/1', $form->getUri());
+        $client->submit($form, [
+            'system_configuration_form_customer' => [
+                'configuration' => [
+                    ['name' => 'defaults.customer.timezone', 'value' => 'Atlantic/Canary'],
+                    ['name' => 'defaults.customer.country', 'value' => 'BB'],
+                    ['name' => 'defaults.customer.currency', 'value' => 'GBP'],
+                ]
+            ]
+        ]);
+
+        $this->assertIsRedirect($client, $this->createUrl('/admin/system-config/edit/customer'));
+        $client->followRedirect();
+        $this->assertTrue($client->getResponse()->isSuccessful());
+        $this->assertHasFlashSaveSuccess($client);
+    }
+
     public function testUpdateUserConfig()
     {
         $client = $this->getClientForAuthenticatedUser(User::ROLE_SUPER_ADMIN);