diff --git a/addons/website_mail_channel/models/mail_channel.py b/addons/website_mail_channel/models/mail_channel.py
index 6778a11f4a20b97033df3ae773268a141ebd5697..3f3428783300678f1291e9d753da531ac6e63e70 100644
--- a/addons/website_mail_channel/models/mail_channel.py
+++ b/addons/website_mail_channel/models/mail_channel.py
@@ -5,8 +5,7 @@ import hmac
 
 from werkzeug import urls
 
-from odoo import api, models
-from odoo.tools.safe_eval import safe_eval
+from odoo import models
 from odoo.addons.http_routing.models.ir_http import slug
 
 
@@ -16,9 +15,9 @@ class MailGroup(models.Model):
     def _notify_email_header_dict(self):
         headers = super(MailGroup, self)._notify_email_header_dict()
         base_url = self.env['ir.config_parameter'].sudo().get_param('web.base.url')
-        headers['List-Archive'] = '<%s/groups/%s>' % (base_url, slug(self)),
-        headers['List-Subscribe'] = '<%s/groups>' % (base_url),
-        headers['List-Unsubscribe'] = '<%s/groups?unsubscribe>' % (base_url,),
+        headers['List-Archive'] = '<%s/groups/%s>' % (base_url, slug(self))
+        headers['List-Subscribe'] = '<%s/groups>' % (base_url)
+        headers['List-Unsubscribe'] = '<%s/groups?unsubscribe>' % (base_url,)
         return headers
 
     def _send_confirmation_email(self, partner_ids, unsubscribe=False):