diff --git a/fcts/languages.py b/fcts/languages.py
index 98144017..b3a7ba35 100644
--- a/fcts/languages.py
+++ b/fcts/languages.py
@@ -63,7 +63,7 @@ async def tr(self, source: SourceType, string_id: str, **args):
             else:
                 used_langs = await self.bot.get_cog('Utilities').get_languages(recipient, limit=1)
                 lang_opt = used_langs[0][0] if len(used_langs) > 0 else self.default_language
-        else:
+        elif isinstance(source, int):
             # get lang from server ID
             lang_id = await self.bot.get_config(source, "language")
             if lang_id is None:
@@ -71,6 +71,8 @@ async def tr(self, source: SourceType, string_id: str, **args):
             else:
                 lang_opt = self.languages[lang_id]
                 self.serv_opts[source] = lang_opt
+        else:
+            raise TypeError(f"Unknown type for translation source: {type(source)}")
         if lang_opt not in self.languages:
             # if lang not known: fallback to default
             lang_opt = self.default_language
diff --git a/fcts/utilities.py b/fcts/utilities.py
index 3f57a8b2..f566d647 100644
--- a/fcts/utilities.py
+++ b/fcts/utilities.py
@@ -65,6 +65,9 @@ async def global_check(self, ctx: MyContext):
                 return True
             return False
         if await self.bot.check_axobot_presence(ctx=ctx):
+            if ctx.prefix.strip() == self.bot.user.mention:
+                invite = 'http://discord.gg/N55zY88'
+                await ctx.send(await self.bot._(ctx.guild.id, "errors.zbot-migration", invite=invite))
             return False
         if not isinstance(ctx, commands.Context) or self.config is None:
             return True
diff --git a/lang/errors/en.json b/lang/errors/en.json
index 6421e23f..38db2c5d 100644
--- a/lang/errors/en.json
+++ b/lang/errors/en.json
@@ -35,5 +35,6 @@
     "rolenotfound": "Unable to find the role `%{r}`",
     "toomanytxtchan": "You have too many accessible text channels",
     "unknown": "Oops, an error occurred :confused: Try again later, or contact support (command `about`).",
-    "usernotfound": "Unable to find the user `%{u}` :confused:"
+    "usernotfound": "Unable to find the user `%{u}` :confused:",
+    "zbot-migration": "This server now use Axobot, the new identity of Zbot. If you need help with the migration, don't hesitate to ask us at <%{invite}>!"
 }
\ No newline at end of file
diff --git a/lang/errors/fr.json b/lang/errors/fr.json
index 28a748a9..d9925e42 100644
--- a/lang/errors/fr.json
+++ b/lang/errors/fr.json
@@ -35,5 +35,6 @@
     "rolenotfound": "Impossible de trouver le rôle `%{r}`",
     "toomanytxtchan": "Vous avez trop de salons textuels accessibles",
     "unknown": "Oups, une erreur est survenue :confused: Réessayez plus tard, ou contactez le support (commande `about`).",
-    "usernotfound": "Impossible de trouver l'utilisateur `%{u}` :confused:"
+    "usernotfound": "Impossible de trouver l'utilisateur `%{u}` :confused:",
+    "zbot-migration": "Ce serveur utilise désormais Axobot, la nouvelle identité de Zbot. Si vous avez besoin d'aide pour la migration, n'hésitez pas à nous demander à <%{invite}> !"
 }
\ No newline at end of file