diff --git a/phpBB/phpbb/db/migration/data/v330/add_mention_settings.php b/phpBB/phpbb/db/migration/data/v330/add_mention_settings.php
deleted file mode 100644
index c0e9a8cf58..0000000000
--- a/phpBB/phpbb/db/migration/data/v330/add_mention_settings.php
+++ /dev/null
@@ -1,43 +0,0 @@
-<?php
-/**
-*
-* This file is part of the phpBB Forum Software package.
-*
-* @copyright (c) phpBB Limited <https://www.phpbb.com>
-* @license GNU General Public License, version 2 (GPL-2.0)
-*
-* For full copyright and license information, please see
-* the docs/CREDITS.txt file.
-*
-*/
-
-namespace phpbb\db\migration\data\v330;
-
-class add_mention_settings extends \phpbb\db\migration\migration
-{
-	public function update_data()
-	{
-		return array(
-			array('config.add', array('allow_mentions', true)),
-			array('config.add', array('mention_batch_size', 50)),
-			array('config.add', array('mention_names_limit', 10)),
-
-			// Set up user permissions
-			array('permission.add', array('u_mention', true)),
-			array('permission.permission_set', array('ROLE_USER_FULL', 'u_mention')),
-			array('permission.permission_set', array('ROLE_USER_STANDARD', 'u_mention')),
-			array('permission.permission_set', array('ROLE_USER_LIMITED', 'u_mention')),
-			array('permission.permission_set', array('ROLE_USER_NOPM', 'u_mention')),
-			array('permission.permission_set', array('ROLE_USER_NOAVATAR', 'u_mention')),
-
-			// Set up forum permissions
-			array('permission.add', array('f_mention', false)),
-			array('permission.permission_set', array('ROLE_FORUM_FULL', 'f_mention')),
-			array('permission.permission_set', array('ROLE_FORUM_STANDARD', 'f_mention')),
-			array('permission.permission_set', array('ROLE_FORUM_LIMITED', 'f_mention')),
-			array('permission.permission_set', array('ROLE_FORUM_ONQUEUE', 'f_mention')),
-			array('permission.permission_set', array('ROLE_FORUM_POLLS', 'f_mention')),
-			array('permission.permission_set', array('ROLE_FORUM_LIMITED_POLLS', 'f_mention')),
-		);
-	}
-}
diff --git a/phpBB/phpbb/db/migration/data/v400/add_mention_settings.php b/phpBB/phpbb/db/migration/data/v400/add_mention_settings.php
new file mode 100644
index 0000000000..7aa2588722
--- /dev/null
+++ b/phpBB/phpbb/db/migration/data/v400/add_mention_settings.php
@@ -0,0 +1,88 @@
+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+namespace phpbb\db\migration\data\v400;
+
+class add_mention_settings extends \phpbb\db\migration\migration
+{
+	public static function depends_on()
+	{
+		return ['\phpbb\db\migration\data\v400\dev'];
+	}
+
+	public function effectively_installed(): bool
+	{
+		return $this->config->offsetExists('allow_mentions')
+			&& $this->config->offsetExists('mention_batch_size')
+			&& $this->config->offsetExists('mention_names_limit');
+	}
+
+	public function update_data()
+	{
+		return [
+			['config.add', ['allow_mentions', true]],
+			['config.add', ['mention_batch_size', 50]],
+			['config.add', ['mention_names_limit', 10]],
+
+			// Set up user permissions
+			['permission.add', ['u_mention', true]],
+			['if', [
+				['permission.role_exists', ['ROLE_USER_FULL']],
+				['permission.permission_set', ['ROLE_USER_FULL', 'u_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_USER_STANDARD']],
+				['permission.permission_set', ['ROLE_USER_STANDARD', 'u_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_USER_LIMITED']],
+				['permission.permission_set', ['ROLE_USER_LIMITED', 'u_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_USER_NOPM']],
+				['permission.permission_set', ['ROLE_USER_NOPM', 'u_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_USER_NOAVATAR']],
+				['permission.permission_set', ['ROLE_USER_NOAVATAR', 'u_mention']],
+			]],
+
+			// Set up forum permissions
+			['permission.add', ['f_mention', false]],
+			['if', [
+				['permission.role_exists', ['ROLE_FORUM_FULL']],
+				['permission.permission_set', ['ROLE_FORUM_FULL', 'f_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_FORUM_STANDARD']],
+				['permission.permission_set', ['ROLE_FORUM_STANDARD', 'f_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_FORUM_LIMITED']],
+				['permission.permission_set', ['ROLE_FORUM_LIMITED', 'f_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_FORUM_ONQUEUE']],
+				['permission.permission_set', ['ROLE_FORUM_ONQUEUE', 'f_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_FORUM_POLLS']],
+				['permission.permission_set', ['ROLE_FORUM_POLLS', 'f_mention']],
+			]],
+			['if', [
+				['permission.role_exists', ['ROLE_FORUM_LIMITED_POLLS']],
+				['permission.permission_set', ['ROLE_FORUM_LIMITED_POLLS', 'f_mention']],
+			]],
+		];
+	}
+}
diff --git a/phpBB/phpbb/db/migration/data/v400/add_storage_permission.php b/phpBB/phpbb/db/migration/data/v400/add_storage_permission.php
index 3689764c72..7018d66801 100644
--- a/phpBB/phpbb/db/migration/data/v400/add_storage_permission.php
+++ b/phpBB/phpbb/db/migration/data/v400/add_storage_permission.php
@@ -43,7 +43,10 @@ class add_storage_permission extends migration
 			['permission.add', ['a_storage']],
 
 			// Set permissions
-			['permission.permission_set', ['ROLE_ADMIN_FULL', 'a_storage']],
+			['if', [
+				['permission.role_exists', ['ROLE_ADMIN_FULL']],
+				['permission.permission_set', ['ROLE_ADMIN_FULL', 'a_storage']],
+			]],
 		];
 	}
 }
diff --git a/phpBB/phpbb/db/migration/tool/permission.php b/phpBB/phpbb/db/migration/tool/permission.php
index 80d64b403a..69f32fcb4c 100644
--- a/phpBB/phpbb/db/migration/tool/permission.php
+++ b/phpBB/phpbb/db/migration/tool/permission.php
@@ -256,6 +256,18 @@ class permission implements \phpbb\db\migration\tool\tool_interface
 		$role_id = (int) $this->db->sql_fetchfield('role_id');
 		$this->db->sql_freeresult($result);
 
+		// Try falling back to searching by role description for standard role titles
+		if (!$role_id && preg_match('/ROLE_(?<title>([A-Z]+_?)+)/', $role_name, $matches))
+		{
+			$role_description = 'ROLE_DESCRIPTION_' . $matches['title'];
+			$sql = 'SELECT role_id
+				FROM ' . ACL_ROLES_TABLE . "
+				WHERE role_description = '" . $this->db->sql_escape($role_description) . "'";
+			$result = $this->db->sql_query($sql);
+			$role_id = (int) $this->db->sql_fetchfield('role_id');
+			$this->db->sql_freeresult($result);
+		}
+
 		return $role_id;
 	}