diff --git a/tox.ini b/tox.ini
index 477fa1c..e49332d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,6 +6,7 @@ commands =
     {envpython} -V
     {envpython} -m compileall speedtest.py
     {envpython} speedtest.py
+    sh -c "{envpython} speedtest.py --source 127.0.0.1 || (( $? == 1 ))"
 
 [testenv:flake8]
 basepython=python
@@ -19,3 +20,4 @@ commands =
     pypy -V
     pypy -m compileall speedtest.py
     pypy speedtest.py
+    sh -c "pypy speedtest.py --source 127.0.0.1 || (( $? == 1 ))"