diff --git a/core/admin/mailu/internal/views/rspamd.py b/core/admin/mailu/internal/views/rspamd.py
index 3d3f8719..e2e453ad 100644
--- a/core/admin/mailu/internal/views/rspamd.py
+++ b/core/admin/mailu/internal/views/rspamd.py
@@ -29,4 +29,4 @@ def rspamd_dkim_key(domain_name):
 @internal.route("/rspamd/local_domains", methods=['GET'])
 def rspamd_local_domains():
     domains = set(models.Domain.query.all() + models.Alternative.query.all())
-    return '\n'.join(domains)
+    return '\n'.join(map(str,domains))