diff --git a/phpBB/config/notifications.yml b/phpBB/config/notifications.yml
index 87a619661c..6fecae2aeb 100644
--- a/phpBB/config/notifications.yml
+++ b/phpBB/config/notifications.yml
@@ -104,7 +104,7 @@ services:
             - { name: notification.type }
 
     notification.type.group_request:
-        class: phpbb_notification_type_group_request
+        class: phpbb\notification\type\group_request
         scope: prototype # scope MUST be prototype for this to work!
         arguments:
             - @user_loader
@@ -122,7 +122,7 @@ services:
             - { name: notification.type }
 
     notification.type.group_request_approved:
-        class: phpbb_notification_type_group_request_approved
+        class: phpbb\notification\type\group_request_approved
         scope: prototype # scope MUST be prototype for this to work!
         arguments:
             - @user_loader
diff --git a/phpBB/install/index.php b/phpBB/install/index.php
index e94c393922..ebfec4232f 100644
--- a/phpBB/install/index.php
+++ b/phpBB/install/index.php
@@ -108,11 +108,11 @@ phpbb_include_updated('includes/utf/utf_tools.' . $phpEx);
 phpbb_require_updated('includes/functions_install.' . $phpEx);
 
 // Setup class loader first
-$phpbb_class_loader_new = new \phpbb\class_loader('phpbb_', "{$phpbb_root_path}install/update/new/phpbb/", $phpEx);
+$phpbb_class_loader_new = new \phpbb\class_loader('phpbb\\', "{$phpbb_root_path}install/update/new/phpbb/", $phpEx);
 $phpbb_class_loader_new->register();
-$phpbb_class_loader = new \phpbb\class_loader('phpbb_', "{$phpbb_root_path}phpbb/", $phpEx);
+$phpbb_class_loader = new \phpbb\class_loader('phpbb\\', "{$phpbb_root_path}phpbb/", $phpEx);
 $phpbb_class_loader->register();
-$phpbb_class_loader_ext = new \phpbb\class_loader('phpbb_ext_', "{$phpbb_root_path}ext/", $phpEx);
+$phpbb_class_loader_ext = new \phpbb\class_loader('phpbb\\ext\\', "{$phpbb_root_path}ext/", $phpEx);
 $phpbb_class_loader_ext->register();
 
 // Set up container
diff --git a/phpBB/phpbb/cache/driver/file.php b/phpBB/phpbb/cache/driver/file.php
index 6e63b6a716..a64232400b 100644
--- a/phpBB/phpbb/cache/driver/file.php
+++ b/phpBB/phpbb/cache/driver/file.php
@@ -260,7 +260,7 @@ class file extends \phpbb\cache\driver\base
 	{
 		try
 		{
-			$iterator = new DirectoryIterator($dir);
+			$iterator = new \DirectoryIterator($dir);
 		}
 		catch (Exception $e)
 		{
diff --git a/phpBB/phpbb/db/migration/data/310/auth_provider_oauth.php b/phpBB/phpbb/db/migration/data/v310/auth_provider_oauth.php
similarity index 93%
rename from phpBB/phpbb/db/migration/data/310/auth_provider_oauth.php
rename to phpBB/phpbb/db/migration/data/v310/auth_provider_oauth.php
index cad1c16bb2..971a7e8504 100644
--- a/phpBB/phpbb/db/migration/data/310/auth_provider_oauth.php
+++ b/phpBB/phpbb/db/migration/data/v310/auth_provider_oauth.php
@@ -7,7 +7,9 @@
 *
 */
 
-class phpbb_db_migration_data_310_auth_provider_oauth extends phpbb_db_migration
+namespace phpbb\db\migration\data\v310;
+
+class auth_provider_oauth extends \phpbb\db\migration\migration
 {
 	public function effectively_installed()
 	{
diff --git a/phpBB/phpbb/db/migration/data/310/mod_rewrite.php b/phpBB/phpbb/db/migration/data/v310/mod_rewrite.php
similarity index 71%
rename from phpBB/phpbb/db/migration/data/310/mod_rewrite.php
rename to phpBB/phpbb/db/migration/data/v310/mod_rewrite.php
index 85ce25abf3..ffb790b135 100644
--- a/phpBB/phpbb/db/migration/data/310/mod_rewrite.php
+++ b/phpBB/phpbb/db/migration/data/v310/mod_rewrite.php
@@ -7,12 +7,14 @@
 *
 */
 
-class phpbb_db_migration_data_310_mod_rewrite extends phpbb_db_migration
+namespace phpbb\db\migration\data\v310;
+
+class mod_rewrite extends \phpbb\db\migration\migration
 {
 	static public function depends_on()
 	{
 		return array(
-			'phpbb_db_migration_data_310_dev',
+			'\phpbb\db\migration\data\v310\dev',
 		);
 	}
 
diff --git a/phpBB/phpbb/db/migration/data/310/notifications_cron.php b/phpBB/phpbb/db/migration/data/v310/notifications_cron.php
similarity index 75%
rename from phpBB/phpbb/db/migration/data/310/notifications_cron.php
rename to phpBB/phpbb/db/migration/data/v310/notifications_cron.php
index 454628e50e..d5fa9c58a5 100644
--- a/phpBB/phpbb/db/migration/data/310/notifications_cron.php
+++ b/phpBB/phpbb/db/migration/data/v310/notifications_cron.php
@@ -7,11 +7,13 @@
 *
 */
 
-class phpbb_db_migration_data_310_notifications_cron extends phpbb_db_migration
+namespace phpbb\db\migration\data\v310;
+
+class notifications_cron extends \phpbb\db\migration\migration
 {
 	static public function depends_on()
 	{
-		return array('phpbb_db_migration_data_310_notifications');
+		return array('\phpbb\db\migration\data\v310\notifications');
 	}
 
 	public function update_data()
diff --git a/phpBB/phpbb/db/migration/data/310/softdelete_mcp_modules.php b/phpBB/phpbb/db/migration/data/v310/softdelete_mcp_modules.php
similarity index 83%
rename from phpBB/phpbb/db/migration/data/310/softdelete_mcp_modules.php
rename to phpBB/phpbb/db/migration/data/v310/softdelete_mcp_modules.php
index f80f55d19a..2db9780601 100644
--- a/phpBB/phpbb/db/migration/data/310/softdelete_mcp_modules.php
+++ b/phpBB/phpbb/db/migration/data/v310/softdelete_mcp_modules.php
@@ -7,7 +7,9 @@
 *
 */
 
-class phpbb_db_migration_data_310_softdelete_mcp_modules extends phpbb_db_migration
+namespace phpbb\db\migration\data\v310;
+
+class softdelete_mcp_modules extends \phpbb\db\migration\migration
 {
 	public function effectively_installed()
 	{
@@ -26,8 +28,8 @@ class phpbb_db_migration_data_310_softdelete_mcp_modules extends phpbb_db_migrat
 	static public function depends_on()
 	{
 		return array(
-			'phpbb_db_migration_data_310_dev',
-			'phpbb_db_migration_data_310_softdelete_p2',
+			'phpbb\db\migration\data\v310\dev',
+			'phpbb\db\migration\data\v310\softdelete_p2',
 		);
 	}