diff --git a/administrator/components/com_admin/sql/updates/mysql/5.4.0-2025-04-23.sql b/administrator/components/com_admin/sql/updates/mysql/5.4.0-2025-04-23.sql
index a806087e70d86..07626abdce1ee 100644
--- a/administrator/components/com_admin/sql/updates/mysql/5.4.0-2025-04-23.sql
+++ b/administrator/components/com_admin/sql/updates/mysql/5.4.0-2025-04-23.sql
@@ -1,2 +1,2 @@
 INSERT INTO `#__extensions` (`package_id`, `name`, `type`, `element`, `folder`, `client_id`, `enabled`, `access`, `protected`, `locked`, `manifest_cache`, `params`, `custom_data`, `ordering`, `state`) VALUES
-(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', -1, 0);
+(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{"classes_aliases":"1","legacy_classes":"1"}', '', -1, 0);
diff --git a/administrator/components/com_admin/sql/updates/postgresql/5.4.0-2025-04-23.sql b/administrator/components/com_admin/sql/updates/postgresql/5.4.0-2025-04-23.sql
index 7252ac4a984ad..291e5f947bba5 100644
--- a/administrator/components/com_admin/sql/updates/postgresql/5.4.0-2025-04-23.sql
+++ b/administrator/components/com_admin/sql/updates/postgresql/5.4.0-2025-04-23.sql
@@ -1,2 +1,2 @@
 INSERT INTO "#__extensions" ("package_id", "name", "type", "element", "folder", "client_id", "enabled", "access", "protected", "locked", "manifest_cache", "params", "custom_data", "ordering", "state") VALUES
-(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', -1, 0);
+(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{"classes_aliases":"1","legacy_classes":"1"}', '', -1, 0);
diff --git a/installation/sql/mysql/base.sql b/installation/sql/mysql/base.sql
index e2cdf5a5a4f34..f8e23bb2c1f17 100644
--- a/installation/sql/mysql/base.sql
+++ b/installation/sql/mysql/base.sql
@@ -263,7 +263,7 @@ INSERT INTO `#__extensions` (`package_id`, `name`, `type`, `element`, `folder`,
 (0, 'plg_authentication_joomla', 'plugin', 'joomla', 'authentication', 0, 1, 1, 1, 1, '', '', '', 2, 0),
 (0, 'plg_authentication_ldap', 'plugin', 'ldap', 'authentication', 0, 0, 1, 0, 1, '', '{"host":"","port":"389","use_ldapV3":"0","negotiate_tls":"0","no_referrals":"0","auth_method":"bind","base_dn":"","search_string":"","users_dn":"","username":"admin","password":"bobby7","ldap_fullname":"fullName","ldap_email":"mail","ldap_uid":"uid"}', '', 3, 0),
 (0, 'plg_behaviour_compat', 'plugin', 'compat', 'behaviour', 0, 1, 1, 0, 1, '', '{"classes_aliases":"1","es5_assets":"1"}', '', 1, 0),
-(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', 2, 0),
+(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{"classes_aliases":"1","legacy_classes":"1"}', '', 2, 0),
 (0, 'plg_behaviour_taggable', 'plugin', 'taggable', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', 3, 0),
 (0, 'plg_behaviour_versionable', 'plugin', 'versionable', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', 4, 0),
 (0, 'plg_content_confirmconsent', 'plugin', 'confirmconsent', 'content', 0, 0, 1, 0, 1, '', '{}', '', 1, 0),
diff --git a/installation/sql/postgresql/base.sql b/installation/sql/postgresql/base.sql
index 7e3223aa46024..f209a95fd0cc2 100644
--- a/installation/sql/postgresql/base.sql
+++ b/installation/sql/postgresql/base.sql
@@ -269,7 +269,7 @@ INSERT INTO "#__extensions" ("package_id", "name", "type", "element", "folder",
 (0, 'plg_authentication_joomla', 'plugin', 'joomla', 'authentication', 0, 1, 1, 1, 1, '', '', '', 2, 0),
 (0, 'plg_authentication_ldap', 'plugin', 'ldap', 'authentication', 0, 0, 1, 0, 1, '', '{"host":"","port":"389","use_ldapV3":"0","negotiate_tls":"0","no_referrals":"0","auth_method":"bind","base_dn":"","search_string":"","users_dn":"","username":"admin","password":"bobby7","ldap_fullname":"fullName","ldap_email":"mail","ldap_uid":"uid"}', '', 3, 0),
 (0, 'plg_behaviour_compat', 'plugin', 'compat', 'behaviour', 0, 1, 1, 0, 1, '', '{"classes_aliases":"1","es5_assets":"1"}', '', 1, 0),
-(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', 2, 0),
+(0, 'plg_behaviour_compat6', 'plugin', 'compat6', 'behaviour', 0, 1, 1, 0, 1, '', '{"classes_aliases":"1","legacy_classes":"1"}', '', 2, 0),
 (0, 'plg_behaviour_taggable', 'plugin', 'taggable', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', 3, 0),
 (0, 'plg_behaviour_versionable', 'plugin', 'versionable', 'behaviour', 0, 1, 1, 0, 1, '', '{}', '', 4, 0),
 (0, 'plg_content_confirmconsent', 'plugin', 'confirmconsent', 'content', 0, 0, 1, 0, 1, '', '{}', '', 1, 0),