diff --git a/app/api/views/custom_domain.py b/app/api/views/custom_domain.py
index 98bfe5bd..ae1873a7 100644
--- a/app/api/views/custom_domain.py
+++ b/app/api/views/custom_domain.py
@@ -10,6 +10,7 @@ def custom_domain_to_dict(custom_domain: CustomDomain):
         "id": custom_domain.id,
         "domain": custom_domain.domain,
         "verified": custom_domain.verified,
+        "nb_alias": custom_domain.nb_alias(),
     }
 
 
diff --git a/docs/api.md b/docs/api.md
index 69a29ec8..b9c38ba9 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -639,11 +639,13 @@ List of custom domains.
     {
       "domain": "test1.org",
       "id": 1,
+      "nb_alias": 0,
       "verified": true
     },
     {
       "domain": "test2.org",
       "id": 2,
+      "nb_alias": 0,
       "verified": false
     }
   ]
diff --git a/tests/api/test_custom_domain.py b/tests/api/test_custom_domain.py
index 1a4cf680..a254544e 100644
--- a/tests/api/test_custom_domain.py
+++ b/tests/api/test_custom_domain.py
@@ -19,7 +19,7 @@ def test_get_custom_domains(flask_client):
     assert r.status_code == 200
     assert r.json == {
         "custom_domains": [
-            {"domain": "test1.org", "id": 1, "verified": True},
-            {"domain": "test2.org", "id": 2, "verified": False},
+            {"domain": "test1.org", "id": 1, "nb_alias": 0, "verified": True},
+            {"domain": "test2.org", "id": 2, "nb_alias": 0, "verified": False},
         ]
     }