diff --git a/tox.ini b/tox.ini
index 5b055b0d..6705f31e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -18,9 +18,9 @@ allowlist_externals = bash
 deps = future
 
 [testenv:style]
+sitepackages = False
 deps =
     pep8
-    future
     flake8
 commands =
     python ./tools/cpep8.py {posargs}