diff --git a/system_tests/app_engine_test_app/main.py b/system_tests/app_engine_test_app/main.py
index c7b89ab..122b505 100644
--- a/system_tests/app_engine_test_app/main.py
+++ b/system_tests/app_engine_test_app/main.py
@@ -15,8 +15,8 @@
 """App Engine standard application that runs basic system tests for
 google.auth.app_engine.
 
-This application has to run tests manually instead of using py.test because
-py.test currently doesn't work on App Engine standard.
+This application has to run tests manually instead of using pytest because
+pytest currently doesn't work on App Engine standard.
 """
 
 import contextlib
diff --git a/tox.ini b/tox.ini
index be124e6..1c52c4b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,12 +16,12 @@
   cryptography
   grpcio; platform_python_implementation != 'PyPy'
 commands =
-  py.test --cov=google.auth --cov=google.oauth2 --cov=tests {posargs:tests}
+  pytest --cov=google.auth --cov=google.oauth2 --cov=tests {posargs:tests}
 
 [testenv:cover]
 basepython = python3.6
 commands =
-  py.test --cov=google.auth --cov=google.oauth2 --cov=tests --cov-report= tests
+  pytest --cov=google.auth --cov=google.oauth2 --cov=tests --cov-report= tests
   coverage report --show-missing --fail-under=100
 deps =
   {[testenv]deps}