diff --git a/invenio_accounts/datastore.py b/invenio_accounts/datastore.py
index 98808247..5f0c2fb7 100644
--- a/invenio_accounts/datastore.py
+++ b/invenio_accounts/datastore.py
@@ -113,6 +113,9 @@ def find_role_by_id(self, role_id):
 
     def find_domain(self, domain_or_id):
         """Find a domain by value or ID."""
+        if domain_or_id is None:
+            return None
+
         if isinstance(domain_or_id, str):
             if domain_or_id.isdigit():
                 clause = Domain.id == int(domain_or_id)