diff --git a/readthedocs/core/middleware.py b/readthedocs/core/middleware.py
index f5f060d7294..de5da624980 100644
--- a/readthedocs/core/middleware.py
+++ b/readthedocs/core/middleware.py
@@ -57,15 +57,15 @@ def process_request(self, request):
                 request.session = SessionBase()  # create an empty session
                 return
 
-        if settings.SESSION_COOKIE_SAMESITE:
-            super().process_request(request)
-        else:
+        if settings.SESSION_COOKIE_SAMESITE == "None":
             if settings.SESSION_COOKIE_NAME in request.COOKIES:
                 session_key = request.COOKIES.get(settings.SESSION_COOKIE_NAME)
             else:
                 session_key = request.COOKIES.get(self.cookie_name_fallback)
 
             request.session = self.SessionStore(session_key)
+        else:
+            super().process_request(request)
 
     def process_response(self, request, response):
         for url in self.IGNORE_URLS:
@@ -139,7 +139,7 @@ def process_response(self, request, response):
                         )
 
                         # NOTE: This was added to support the fallback cookie
-                        if not settings.SESSION_COOKIE_SAMESITE:
+                        if settings.SESSION_COOKIE_SAMESITE == "None":
                             # Forcibly set the session cookie to SameSite=None
                             # This isn't supported in Django<3.1
                             # https://github.com/django/django/pull/11894
@@ -157,7 +157,8 @@ def process_response(self, request, response):
                                 path=settings.SESSION_COOKIE_PATH,
                                 secure=settings.SESSION_COOKIE_SECURE or None,
                                 httponly=settings.SESSION_COOKIE_HTTPONLY or None,
-                                samesite=settings.SESSION_COOKIE_SAMESITE,
+                                # Use browser default in case SameSite=None is rejected.
+                                samesite=False,
                             )
         return response
 
diff --git a/readthedocs/rtd_tests/tests/test_middleware.py b/readthedocs/rtd_tests/tests/test_middleware.py
index 9abce650fe1..698370a911b 100644
--- a/readthedocs/rtd_tests/tests/test_middleware.py
+++ b/readthedocs/rtd_tests/tests/test_middleware.py
@@ -250,7 +250,7 @@ def setUp(self):
 
         self.user = create_user(username="owner", password="test")
 
-    @override_settings(SESSION_COOKIE_SAMESITE=None)
+    @override_settings(SESSION_COOKIE_SAMESITE="None")
     def test_fallback_cookie(self):
         request = self.factory.get("/")
         response = HttpResponse()
@@ -261,7 +261,7 @@ def test_fallback_cookie(self):
         self.assertTrue(settings.SESSION_COOKIE_NAME in response.cookies)
         self.assertTrue(self.middleware.cookie_name_fallback in response.cookies)
 
-    @override_settings(SESSION_COOKIE_SAMESITE=None)
+    @override_settings(SESSION_COOKIE_SAMESITE="None")
     def test_main_cookie_samesite_none(self):
         request = self.factory.get("/")
         response = HttpResponse()
diff --git a/readthedocs/settings/base.py b/readthedocs/settings/base.py
index 8a27fccb5d9..0cef49e51fc 100644
--- a/readthedocs/settings/base.py
+++ b/readthedocs/settings/base.py
@@ -109,7 +109,7 @@ def SESSION_COOKIE_SAMESITE(self):
         Cookie used in cross-origin API requests from *.rtd.io to rtd.org/api/v2/sustainability/.
         """
         if self.USE_PROMOS:
-            return None
+            return "None"
         # This is django's default.
         return "Lax"
 
diff --git a/readthedocs/settings/proxito/base.py b/readthedocs/settings/proxito/base.py
index 78f3badd3ef..d700089df98 100644
--- a/readthedocs/settings/proxito/base.py
+++ b/readthedocs/settings/proxito/base.py
@@ -16,7 +16,7 @@ class CommunityProxitoSettingsMixin:
 
     # Allow cookies from cross-site requests on subdomains for now.
     # As 'Lax' breaks when the page is embedded in an iframe.
-    SESSION_COOKIE_SAMESITE = None
+    SESSION_COOKIE_SAMESITE = "None"
 
     @property
     def DATABASES(self):