diff --git a/core/core.services.yml b/core/core.services.yml
index 6b972c88d4..e038d1c606 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -502,7 +502,7 @@ services:
     class: Drupal\Core\Http\ClientFactory
     arguments: ['@http_handler_stack']
   plugin.manager.link_relation_type:
-    class: \Drupal\Core\Http\LinkRelationTypeManager
+    class: Drupal\Core\Http\LinkRelationTypeManager
     arguments: ['%app.root%', '@module_handler', '@cache.discovery']
   theme.negotiator:
     class: Drupal\Core\Theme\ThemeNegotiator
@@ -902,7 +902,7 @@ services:
     class: Drupal\Core\Routing\AccessAwareRouter
     arguments: ['@router.no_access_checks', '@access_manager', '@current_user']
   router.no_access_checks:
-    class: \Drupal\Core\Routing\Router
+    class: Drupal\Core\Routing\Router
     arguments: ['@router.route_provider', '@path.current', '@url_generator']
     tags:
       # @todo Try to combine those tags together, see https://www.drupal.org/node/2915772.
diff --git a/core/modules/big_pipe/big_pipe.services.yml b/core/modules/big_pipe/big_pipe.services.yml
index 09747e887f..2a6f3cf709 100644
--- a/core/modules/big_pipe/big_pipe.services.yml
+++ b/core/modules/big_pipe/big_pipe.services.yml
@@ -14,7 +14,7 @@ services:
     arguments: ['@renderer', '@session', '@request_stack', '@http_kernel', '@event_dispatcher', '@config.factory']
   html_response.attachments_processor.big_pipe:
     public: false
-    class: \Drupal\big_pipe\Render\BigPipeResponseAttachmentsProcessor
+    class: Drupal\big_pipe\Render\BigPipeResponseAttachmentsProcessor
     decorates: html_response.attachments_processor
     arguments: ['@html_response.attachments_processor.big_pipe.inner', '@asset.resolver', '@config.factory', '@asset.css.collection_renderer', '@asset.js.collection_renderer', '@request_stack', '@renderer', '@module_handler', '@language_manager']
 
diff --git a/core/modules/block_content/block_content.services.yml b/core/modules/block_content/block_content.services.yml
index 9c6dceb82e..9c68f0ff96 100644
--- a/core/modules/block_content/block_content.services.yml
+++ b/core/modules/block_content/block_content.services.yml
@@ -1,6 +1,6 @@
 services:
   block_content.uuid_lookup:
-    class: \Drupal\block_content\BlockContentUuidLookup
+    class: Drupal\block_content\BlockContentUuidLookup
     arguments: ['@cache.bootstrap', '@lock', '@entity_type.manager']
     tags:
       - { name: needs_destruction }
diff --git a/core/modules/rest/rest.services.yml b/core/modules/rest/rest.services.yml
index 868a048f92..d8c3064b27 100644
--- a/core/modules/rest/rest.services.yml
+++ b/core/modules/rest/rest.services.yml
@@ -24,7 +24,7 @@ services:
       - { name: event_subscriber }
     arguments: ['@serializer', '@renderer', '@current_route_match']
   rest.resource.entity.post_route.subscriber:
-    class: \Drupal\rest\EventSubscriber\EntityResourcePostRouteSubscriber
+    class: Drupal\rest\EventSubscriber\EntityResourcePostRouteSubscriber
     arguments: ['@entity_type.manager']
     tags:
       - { name: event_subscriber }
diff --git a/core/modules/serialization/serialization.services.yml b/core/modules/serialization/serialization.services.yml
index a5c6f67a72..d29c6ab378 100644
--- a/core/modules/serialization/serialization.services.yml
+++ b/core/modules/serialization/serialization.services.yml
@@ -65,7 +65,7 @@ services:
       # Priority must be higher than serializer.normalizer.primitive_data.
       - { name: normalizer, priority: 20 }
   serializer.normalizer.datetimeiso8601:
-    class: \Drupal\serialization\Normalizer\DateTimeIso8601Normalizer
+    class: Drupal\serialization\Normalizer\DateTimeIso8601Normalizer
     arguments: ['@config.factory']
     tags:
       # Priority must be higher than serializer.normalizer.primitive_data.
diff --git a/core/modules/system/tests/modules/lazy_route_provider_install_test/lazy_route_provider_install_test.services.yml b/core/modules/system/tests/modules/lazy_route_provider_install_test/lazy_route_provider_install_test.services.yml
index 2de99d39e1..d980395477 100644
--- a/core/modules/system/tests/modules/lazy_route_provider_install_test/lazy_route_provider_install_test.services.yml
+++ b/core/modules/system/tests/modules/lazy_route_provider_install_test/lazy_route_provider_install_test.services.yml
@@ -1,5 +1,5 @@
 services:
   plugin.manager.lazy_route_provider_install_test:
-    class: '\Drupal\lazy_route_provider_install_test\PluginManager'
+    class: Drupal\lazy_route_provider_install_test\PluginManager
     parent: default_plugin_manager
     arguments: ['@url_generator']