diff --git a/addons/website_livechat/models/discuss_channel.py b/addons/website_livechat/models/discuss_channel.py
index 4ee509b8ca2..dbf34c5a96d 100644
--- a/addons/website_livechat/models/discuss_channel.py
+++ b/addons/website_livechat/models/discuss_channel.py
@@ -8,7 +8,7 @@ from odoo.exceptions import AccessError
 class DiscussChannel(models.Model):
     _inherit = 'discuss.channel'
 
-    livechat_visitor_id = fields.Many2one('website.visitor', string='Visitor')
+    livechat_visitor_id = fields.Many2one('website.visitor', string='Visitor', index='btree_not_null')
 
     def channel_pin(self, pinned=False):
         """ Override to clean an empty livechat channel.