diff --git a/test/test_session.py b/test/test_session.py
index afea5f6..b8ae074 100644
--- a/test/test_session.py
+++ b/test/test_session.py
@@ -33,9 +33,9 @@
             table_id += 1
 
         # Configure namespaces
-        self.vapi.app_namespace_add_del(namespace_id="0",
+        self.vapi.app_namespace_add_del(namespace_id=b"0",
                                         sw_if_index=self.loop0.sw_if_index)
-        self.vapi.app_namespace_add_del(namespace_id="1",
+        self.vapi.app_namespace_add_del(namespace_id=b"1",
                                         sw_if_index=self.loop1.sw_if_index)
 
     def tearDown(self):