diff --git a/tests/google-cloud-python-system/run_system_tests.sh b/tests/google-cloud-python-system/run_system_tests.sh
index 17d3aac..f9f81a4 100755
--- a/tests/google-cloud-python-system/run_system_tests.sh
+++ b/tests/google-cloud-python-system/run_system_tests.sh
@@ -31,8 +31,8 @@ for package in ${packages}; do
   nox \
     -f "${noxfile}" \
     -e \
-    "system_tests(python_version='2.7')" \
-    "system_tests(python_version='3.6')" \
+    "system(py='2.7')" \
+    "system(py='3.6')" \
     || exit_code=1
 done