diff --git a/chrono/agendas/models.py b/chrono/agendas/models.py
index 8712911f..b4f97953 100644
--- a/chrono/agendas/models.py
+++ b/chrono/agendas/models.py
@@ -304,9 +304,10 @@ class VirtualMember(models.Model):
                 error = True
                 error_msg += [
                     _(
-                        'Meeting type "%s" (%s minutes) (identifier: %s) does no exist.'
-                        % (meetingtype.label, meetingtype.duration, meetingtype.slug)
+                        'Meeting type "%(label)s" (%(duration)s minutes) '
+                        '(identifier: %(slug)s) does no exist.'
                     )
+                    % {'label': meetingtype.label, 'duration': meetingtype.duration, 'slug': meetingtype.slug}
                 ]
         if error:
             raise ValidationError(error_msg)