diff --git a/noxfile.py b/noxfile.py
index 1ac4450..3f01ef1 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -15,7 +15,6 @@
 from __future__ import absolute_import
 import os
 import shutil
-import sys
 
 # https://github.com/google/importlab/issues/25
 import nox  # pytype: disable=import-error
@@ -24,7 +23,7 @@
 
 
 def _greater_or_equal_than_36(version_string):
-    tokens = version_string.split('.')
+    tokens = version_string.split(".")
     for i, token in enumerate(tokens):
         try:
             tokens[i] = int(token)
@@ -72,13 +71,13 @@
         session.run(*pytest_args)
 
 
-@nox.session(python=["2.7", "3.5", "3.6", "3.7", "3.8"])
+@nox.session(python=["2.7", "3.5", "3.6", "3.7", "3.8", "3.9"])
 def unit(session):
     """Run the unit test suite."""
     default(session)
 
 
-@nox.session(python=["2.7", "3.5", "3.6", "3.7", "3.8"])
+@nox.session(python=["2.7", "3.5", "3.6", "3.7", "3.8", "3.9"])
 def unit_grpc_gcp(session):
     """Run the unit test suite with grpcio-gcp installed."""