diff --git a/modoboa/admin/models/mailbox.py b/modoboa/admin/models/mailbox.py
index 6ed568c83..90b6ba261 100644
--- a/modoboa/admin/models/mailbox.py
+++ b/modoboa/admin/models/mailbox.py
@@ -145,7 +145,7 @@ class Mailbox(AdminObject):
             )
             if code:
                 raise lib_exceptions.InternalError(
-                    _("Failed to retrieve mailbox location (%s)" % output))
+                    _(u"Failed to retrieve mailbox location (%s)") % output)
             self.__mail_home = output.strip()
         return self.__mail_home