diff --git a/synthtool/gcp/templates/python_library/noxfile.py.j2 b/synthtool/gcp/templates/python_library/noxfile.py.j2
index 362aca1c7..285356a34 100644
--- a/synthtool/gcp/templates/python_library/noxfile.py.j2
+++ b/synthtool/gcp/templates/python_library/noxfile.py.j2
@@ -436,7 +436,7 @@ def docfx(session):
     )
 
 
-@nox.session(python=SYSTEM_TEST_PYTHON_VERSIONS)
+@nox.session(python="{{ unit_test_python_versions | last }}")
 @nox.parametrize(
     "protobuf_implementation",
     [ "python", "upb", "cpp" ],