diff --git a/addons/crm/models/crm_lead.py b/addons/crm/models/crm_lead.py
index 5226d19d670..068f1623bdd 100644
--- a/addons/crm/models/crm_lead.py
+++ b/addons/crm/models/crm_lead.py
@@ -606,7 +606,7 @@ class Lead(models.Model):
             # check for "same commercial entity" duplicates
             if lead.partner_id and lead.partner_id.commercial_partner_id:
                 duplicate_lead_ids |= lead.with_context(active_test=False).search(common_lead_domain + [
-                    ("partner_id", "child_of", lead.partner_id.commercial_partner_id.id)
+                    ("partner_id", "child_of", lead.partner_id.commercial_partner_id.ids)
                 ])
             # check the phone number duplicates, based on phone_sanitized. Only
             # exact matches are found, and the single one stored in phone_sanitized