diff --git a/portal/locales/en.json b/portal/locales/en.json
index 2d07f11..f145289 100644
--- a/portal/locales/en.json
+++ b/portal/locales/en.json
@@ -30,6 +30,7 @@
    "good_practices_about_user_password": "Pick a user password of at least 8 characters - though it is good practice to use longer ones (i.e. a passphrase) and/or use various kind of characters (uppercase, lowercase, digits and special characters).",
    "wrong_current_password": "The current password is wrong",
    "invalid_mail": "Invalid e-mail address",
+   "obsolete_version": "The version of YunoHost running on this server is obsolete and should be upgraded to YunoHost 4.x / Buster. Please contact your administrator about this.",
    "invalid_domain": "Invalid domain in",
    "invalid_mailforward": "Invalid e-mail forwarding address",
    "mail_already_used": "E-mail address already in use",
diff --git a/portal/portal.html b/portal/portal.html
index c95ab04..4d148ba 100644
--- a/portal/portal.html
+++ b/portal/portal.html
@@ -1,3 +1,5 @@
+<div class="wrapper messages warning">{{t_obsolete_version}}</div>
+
 <div class="ynh-wrapper user">
   <ul class="user-menu">
     <li><a id="ynh-logout" class="icon icon-connexion" href="?action=logout">{{t_logout}}</a></li>