diff --git a/go/routers/app_multiplexer/tests/test_vumi_app.py b/go/routers/app_multiplexer/tests/test_vumi_app.py
index b6f2c4391..eb3008cea 100644
--- a/go/routers/app_multiplexer/tests/test_vumi_app.py
+++ b/go/routers/app_multiplexer/tests/test_vumi_app.py
@@ -3,6 +3,7 @@
 from twisted.internet.defer import inlineCallbacks
 
 from vumi.tests.helpers import VumiTestCase
+
 from go.routers.app_multiplexer.vumi_app import ApplicationMultiplexer
 from go.routers.tests.helpers import RouterWorkerHelper
 
diff --git a/go/routers/app_multiplexer/vumi_app.py b/go/routers/app_multiplexer/vumi_app.py
index 65885ad75..e65d769b3 100644
--- a/go/routers/app_multiplexer/vumi_app.py
+++ b/go/routers/app_multiplexer/vumi_app.py
@@ -85,11 +85,9 @@ def setup_router(self):
         return d
 
     def session_manager(self, config):
-        return SessionManager.from_redis_config(
-            config.redis_manager,
-            key_prefix=':'.join((self.worker_name, config.router.key)),
-            max_session_length=config.session_expiry
-        )
+        key_prefix = ':'.join((self.worker_name, config.router.key))
+        redis = self.redis.sub_manager(key_prefix)
+        return SessionManager(redis, max_session_length=config.session_expiry)
 
     def target_endpoints(self, config):
         """