diff --git a/mellon/sessions_backends/cached_db.py b/mellon/sessions_backends/cached_db.py
index f4cd363..e46c1f6 100644
--- a/mellon/sessions_backends/cached_db.py
+++ b/mellon/sessions_backends/cached_db.py
@@ -15,8 +15,8 @@
 
 from django.contrib.sessions.backends.cached_db import SessionStore as BaseSessionStore
 
-from . import db
+from .db import MellonMixin
 
 
-class SessionStore(db.SessionStore, BaseSessionStore):
+class SessionStore(MellonMixin, BaseSessionStore):
     pass
diff --git a/mellon/sessions_backends/db.py b/mellon/sessions_backends/db.py
index be3b722..bd751d9 100644
--- a/mellon/sessions_backends/db.py
+++ b/mellon/sessions_backends/db.py
@@ -18,11 +18,12 @@ from django.contrib.sessions.backends.db import SessionStore as BaseSessionStore
 from mellon import utils
 
 
-class SessionStore(BaseSessionStore):
+class MellonMixin:
     def get_session_not_on_or_after(self):
-        session_not_on_or_after = self.get('mellon_session', {}).get('session_not_on_or_after')
-        if session_not_on_or_after:
-            return utils.iso8601_to_datetime(session_not_on_or_after)
+        if hasattr(self, '_session_cache'):
+            session_not_on_or_after = self.get('mellon_session', {}).get('session_not_on_or_after')
+            if session_not_on_or_after:
+                return utils.iso8601_to_datetime(session_not_on_or_after)
         return None
 
     def get_expiry_age(self, **kwargs):
@@ -36,3 +37,7 @@ class SessionStore(BaseSessionStore):
         if session_not_on_or_after and 'expiry' not in kwargs:
             kwargs['expiry'] = session_not_on_or_after
         return super().get_expiry_date(**kwargs)
+
+
+class SessionStore(MellonMixin, BaseSessionStore):
+    pass
diff --git a/tests/test_session.py b/tests/test_session.py
new file mode 100644
index 0000000..b129a2a
--- /dev/null
+++ b/tests/test_session.py
@@ -0,0 +1,47 @@
+import datetime
+
+import pytest
+from django.core.cache import cache
+from django.utils.timezone import now
+
+from mellon.sessions_backends import cached_db, db
+
+cls_param = pytest.mark.parametrize('cls', [cached_db.SessionStore, db.SessionStore], ids=['cached_db', 'db'])
+
+
+@cls_param
+def test_basic(db, cls):
+    cls = cached_db.SessionStore
+
+    session1 = cls()
+    session1['foo'] = 'bar'
+    session1.save()
+
+    session = cls(session_key=session1.session_key)
+    assert session['foo'] == 'bar'
+
+    # check with loading from cache
+    cache.clear()
+    session = cls(session_key=session1.session_key)
+    assert session['foo'] == 'bar'
+
+
+@cls_param
+def test_expiry(db, cls, freezer):
+    cls = cached_db.SessionStore
+
+    session1 = cls()
+    session1['foo'] = 'bar'
+    session1['mellon_session'] = {
+        'session_not_on_or_after': (now() + datetime.timedelta(hours=1)).isoformat()
+    }
+    session1.save()
+
+    freezer.tick(3599)
+
+    session = cls(session_key=session1.session_key)
+    assert session['foo'] == 'bar'
+
+    freezer.tick(2)
+    session = cls(session_key=session1.session_key)
+    assert 'foo' not in session