diff --git a/neutron/tests/functional/test_server.py b/neutron/tests/functional/test_server.py
index 01377d3b73e..6ca49533218 100644
--- a/neutron/tests/functional/test_server.py
+++ b/neutron/tests/functional/test_server.py
@@ -228,7 +228,7 @@ class TestWsgiServer(TestNeutronServer):
 
             # Memorize a port that was chosen for the service
             self.port = server.port
-            os.write(self.pipeout, bytes(self.port))
+            os.write(self.pipeout, bytes(str(self.port), 'utf-8'))
 
             server.wait()