diff --git a/tox.ini b/tox.ini
index 44f803d..5dab765 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,12 +11,13 @@ deps = flake8
 
 [testenv]
 commands =
-    ./runtests.sh {posargs}
+    ./runtests.sh -n 4 {posargs}
 deps =
     Flask<1
     mock
     pytest
     pytest-httpbin
+    pytest-xdist
     PyYAML
     requests27: requests==2.7.0
     httplib2: httplib2