diff --git a/phpBB/includes/db/migration/tool/config.php b/phpBB/includes/db/migration/tool/config.php
index 458a25fb66..0b626bf455 100644
--- a/phpBB/includes/db/migration/tool/config.php
+++ b/phpBB/includes/db/migration/tool/config.php
@@ -49,7 +49,7 @@ class phpbb_db_migration_tool_config implements phpbb_db_migration_tool_interfac
 	{
 		if (isset($this->config[$config_name]))
 		{
-			throw new phpbb_db_migration_exception('CONFIG_ALREADY_EXIST', $config_name);
+			return;
 		}
 
 		$this->config->set($config_name, $config_value, !$is_dynamic);
@@ -105,7 +105,7 @@ class phpbb_db_migration_tool_config implements phpbb_db_migration_tool_interfac
 	{
 		if (!isset($this->config[$config_name]))
 		{
-			throw new phpbb_db_migration_exception('CONFIG_NOT_EXIST', $config_name);
+			return;
 		}
 
 		$this->config->delete($config_name);
diff --git a/phpBB/includes/db/migration/tool/module.php b/phpBB/includes/db/migration/tool/module.php
index ad94c5aadb..ec683d36af 100644
--- a/phpBB/includes/db/migration/tool/module.php
+++ b/phpBB/includes/db/migration/tool/module.php
@@ -236,7 +236,7 @@ class phpbb_db_migration_tool_module implements phpbb_db_migration_tool_interfac
 
 		if ($this->exists($class, $parent, $data['module_langname']))
 		{
-			throw new phpbb_db_migration_exception('MODULE_ALREADY_EXIST', $data['module_langname']);
+			return;
 		}
 
 		if (!class_exists('acp_modules'))
@@ -369,7 +369,7 @@ class phpbb_db_migration_tool_module implements phpbb_db_migration_tool_interfac
 		{
 			if (!$this->exists($class, $parent, $module))
 			{
-				throw new phpbb_db_migration_exception('MODULE_NOT_EXIST', ((isset($this->user->lang[$module])) ? $this->user->lang[$module] : $module));
+				return;
 			}
 
 			$parent_sql = '';
@@ -442,7 +442,7 @@ class phpbb_db_migration_tool_module implements phpbb_db_migration_tool_interfac
 				$result = $acp_modules->delete_module($module_id);
 				if (!empty($result))
 				{
-					throw new phpbb_db_migration_exception('MODULE_NOT_REMOVABLE', $module_id, $result);
+					return;
 				}
 			}
 
diff --git a/phpBB/includes/db/migration/tool/permission.php b/phpBB/includes/db/migration/tool/permission.php
index 4231fbe1dd..3b196fdbc2 100644
--- a/phpBB/includes/db/migration/tool/permission.php
+++ b/phpBB/includes/db/migration/tool/permission.php
@@ -107,7 +107,7 @@ class phpbb_db_migration_tool_permission implements phpbb_db_migration_tool_inte
 	{
 		if ($this->exists($auth_option, $global))
 		{
-			throw new phpbb_db_migration_exception('PERMISSION_ALREADY_EXIST', $auth_option);
+			return;
 		}
 
 		// We've added permissions, so set to true to notify the user.
@@ -190,7 +190,7 @@ class phpbb_db_migration_tool_permission implements phpbb_db_migration_tool_inte
 	{
 		if (!$this->exists($auth_option, $global))
 		{
-			throw new phpbb_db_migration_exception('PERMISSION_NOT_EXIST', $auth_option);
+			return;
 		}
 
 		if ($global)
@@ -315,7 +315,7 @@ class phpbb_db_migration_tool_permission implements phpbb_db_migration_tool_inte
 
 		if (!$role_id)
 		{
-			throw new phpbb_db_migration_exception('ROLE_NOT_EXIST', $role_name);
+			return;
 		}
 
 		$sql = 'DELETE FROM ' . ACL_ROLES_DATA_TABLE . '
diff --git a/phpBB/language/en/migrator.php b/phpBB/language/en/migrator.php
index a62da483cf..f94c27be8c 100644
--- a/phpBB/language/en/migrator.php
+++ b/phpBB/language/en/migrator.php
@@ -35,7 +35,6 @@ if (empty($lang) || !is_array($lang))
 // in a url you again do not need to specify an order e.g., 'Click %sHERE%s' is fine
 
 $lang = array_merge($lang, array(
-	'CONFIG_ALREADY_EXIST'				=> 'The config setting "%s" unexpectedly already exists.',
 	'CONFIG_NOT_EXIST'					=> 'The config setting "%s" unexpectedly does not exist.',
 
 	'GROUP_NOT_EXIST'					=> 'The group "%s" unexpectedly does not exist.',
@@ -46,13 +45,10 @@ $lang = array_merge($lang, array(
 	'MIGRATION_NOT_FULFILLABLE'			=> 'The migration "%1$s" is not fulfillable, missing migration "%2$s".',
 	'MIGRATION_SCHEMA_DONE'				=> 'Installed Schema: %s',
 
-	'MODULE_ALREADY_EXIST'				=> 'The module "%s" unexpectedly already exists.',
 	'MODULE_ERROR'						=> 'An error occured while creating a module: %s',
 	'MODULE_INFO_FILE_NOT_EXIST'		=> 'A required module info file is missing: %2$s',
 	'MODULE_NOT_EXIST'					=> 'A required module does not exist: %s',
-	'MODULE_NOT_REMOVABLE'				=> 'Module %1$s was unable to be removed: %2$s',
 
-	'PERMISSION_ALREADY_EXIST'			=> 'The permission setting "%s" unexpectedly already exists.',
 	'PERMISSION_NOT_EXIST'				=> 'The permission setting "%s" unexpectedly does not exist.',
 
 	'ROLE_NOT_EXIST'					=> 'The permission role "%s" unexpectedly does not exist.',