diff --git a/substack/api.py b/substack/api.py
index 6e1dd53..6cf733d 100644
--- a/substack/api.py
+++ b/substack/api.py
@@ -10,9 +10,8 @@
 import os
 from datetime import datetime
 from urllib.parse import urljoin
-
 import requests
-
+from requests.utils import cookiejar_from_dict
 from substack.exceptions import SubstackAPIException, SubstackRequestException
 
 logger = logging.getLogger(__name__)
@@ -64,8 +63,9 @@ def __init__(
         # Load cookies from file if provided
         # Helps with Captcha errors by reusing cookies from "local" auth, then switching to running code in the cloud
         if cookies_path is not None:
-            with open(cookies_path) as f:
-                cookies = json.load(f)
+            with open(cookies_path, "r", encoding="utf-8") as f:
+                raw = json.load(f)
+                cookies = cookiejar_from_dict({c["name"]: c["value"] for c in raw})
             self._session.cookies.update(cookies)
 
         elif email is not None and password is not None:
@@ -189,11 +189,11 @@ def get_publication_url(publication: dict) -> str:
         Args:
             publication:
         """
-        custom_domain = publication["custom_domain"]
-        if not custom_domain:
-            publication_url = f"https://{publication['subdomain']}.substack.com"
-        else:
+        if publication.get('custom_domain_optional', None):
+            custom_domain = publication["custom_domain"]
             publication_url = f"https://{custom_domain}"
+        else:
+            publication_url = f"https://{publication['subdomain']}.substack.com"
 
         return publication_url