diff --git c/core/modules/system/system.routing.yml w/core/modules/system/system.routing.yml
index ae57a16..4867e42 100644
--- c/core/modules/system/system.routing.yml
+++ w/core/modules/system/system.routing.yml
@@ -347,9 +347,9 @@ system.timezone:
   path: '/system/timezone/{abbreviation}/{offset}/{is_daylight_saving_time}'
   defaults:
     _controller: '\Drupal\system\Controller\TimezoneController::getTimezone'
-    abbreviation: null
-    offset: null
-    is_daylight_saving_time: null
+    abbreviation: ''
+    offset: -1
+    is_daylight_saving_time: NULL
   requirements:
     _access: 'TRUE'