diff --git a/substack/api.py b/substack/api.py
index 378eb67..b92fe82 100644
--- a/substack/api.py
+++ b/substack/api.py
@@ -346,7 +346,10 @@ def get_publication_subscriber_count(self):
             f"{self.publication_url}/publication_launch_checklist"
         )
 
-        return Api._handle_response(response=response)["subscriberCount"]
+        data = Api._handle_response(response=response)
+        if "subscriberCount" in data:
+            return data["subscriberCount"]
+        return len(data["subscribers"])
 
     def get_published_posts(
         self, offset=0, limit=25, order_by="post_date", order_direction="desc"
diff --git a/tests/substack/test_api.py b/tests/substack/test_api.py
index 64c5175..d255a60 100644
--- a/tests/substack/test_api.py
+++ b/tests/substack/test_api.py
@@ -40,6 +40,26 @@ def test_api_exception(self):
             with patch("requests.Session.post", return_value=response):
                 Api(email="", password="")
 
+    def test_get_publication_subscriber_count_from_legacy_response(self):
+        api = Api.__new__(Api)
+        api.publication_url = "https://writer.substack.com/api/v1"
+        api._session = Mock()
+        response = Mock(status_code=200)
+        response.json.return_value = {"subscriberCount": 123}
+        api._session.get.return_value = response
+
+        self.assertEqual(api.get_publication_subscriber_count(), 123)
+
+    def test_get_publication_subscriber_count_from_subscribers(self):
+        api = Api.__new__(Api)
+        api.publication_url = "https://writer.substack.com/api/v1"
+        api._session = Mock()
+        response = Mock(status_code=200)
+        response.json.return_value = {"subscribers": [{"id": 1}, {"id": 2}]}
+        api._session.get.return_value = response
+
+        self.assertEqual(api.get_publication_subscriber_count(), 2)
+
     @_e2e
     def test_get_posts(self):
         api = _api_from_env()