diff --git a/locales/en.json b/locales/en.json
index 56db04f46..5e7d59df1 100644
--- a/locales/en.json
+++ b/locales/en.json
@@ -466,9 +466,7 @@
     "migration_0021_general_warning": "Please note that this migration is a delicate operation. The YunoHost team did its best to review and test it, but the migration might still break parts of the system or its apps.\n\nTherefore, it is recommended to:\n    - Perform a backup of any critical data or app. More info on https://yunohost.org/backup;\n    - Be patient after launching the migration: Depending on your Internet connection and hardware, it might take up to a few hours for everything to upgrade.",
     "migration_0021_problematic_apps_warning": "Please note that the following possibly problematic installed apps were detected. It looks like those were not installed from the YunoHost app catalog, or are not flagged as 'working'. Consequently, it cannot be guaranteed that they will still work after the upgrade: {problematic_apps}",
     "migration_0021_modified_files": "Please note that the following files were found to be manually modified and might be overwritten following the upgrade: {manually_modified_files}",
-    "migration_0021_specific_upgrade": "Starting upgrade of system packages that needs to be upgrade independently...",
     "migration_0021_cleaning_up": "Cleaning up cache and packages not useful anymore...",
-    "migration_0021_weak_certs": "The following certificates were found to still use weak signature algorithms and have to be upgraded to be compatible with the next version of nginx: {certs}",
     "migration_0021_patch_yunohost_conflicts": "Applying patch to workaround conflict issue...",
     "migration_0023_postgresql_11_not_installed": "PostgreSQL was not installed on your system. Nothing to do.",
     "migration_0023_postgresql_13_not_installed": "PostgreSQL 11 is installed, but not postgresql 13!? Something weird might have happened on your system :(...",
diff --git a/src/yunohost/data_migrations/0021_migrate_to_bullseye.py b/src/yunohost/data_migrations/0021_migrate_to_bullseye.py
index a5bb1e523..6678fa040 100644
--- a/src/yunohost/data_migrations/0021_migrate_to_bullseye.py
+++ b/src/yunohost/data_migrations/0021_migrate_to_bullseye.py
@@ -177,12 +177,14 @@ class MyMigration(Migration):
         # - replace single 'buster' occurence by 'bulleye'
         # - comments lines containing "backports"
         # - replace 'buster/updates' by 'bullseye/updates' (or same with -)
+        # Special note about the security suite:
+        # https://www.debian.org/releases/bullseye/amd64/release-notes/ch-information.en.html#security-archive
         for f in sources_list:
             command = (
                 f"sed -i {f} "
                 "-e 's@ buster @ bullseye @g' "
                 "-e '/backports/ s@^#*@#@' "
-                "-e 's@ buster/updates @ bullseye/updates @g' "
+                "-e 's@ buster/updates @ bullseye-security @g' "
                 "-e 's@ buster-@ bullseye-@g' "
             )
             os.system(command)