diff --git a/prismic/api.py b/prismic/api.py
index e8935b6..8fa5a06 100644
--- a/prismic/api.py
+++ b/prismic/api.py
@@ -85,7 +85,7 @@ def preview_session(self, token, link_resolver, default_url):
 
         :return: the URL to redirect the user to
         """
-        main_document_id = get_json(token, request_handler=self.request_handler).get("mainDocument")
+        main_document_id = get_json(token, request_handler=self.request_handler, cache=self.cache).get("mainDocument")
         if main_document_id is None:
             return default_url
         response = self.form("everything").ref(token).query(predicates.at("document.id", main_document_id)).submit()
diff --git a/prismic/connection.py b/prismic/connection.py
index 501ba4a..8149062 100644
--- a/prismic/connection.py
+++ b/prismic/connection.py
@@ -66,7 +66,7 @@ def get_json(url, params=None, access_token=None, cache=None, ttl=None, request_
 
 
 def get_max_age(headers):
-    expire_header = headers["Cache-Control"]
+    expire_header = headers.get("Cache-Control")
     if expire_header is not None:
         m = re.match("max-age=(\d+)", expire_header)
         if m: