diff --git a/tox.ini b/tox.ini
index 7de82a4..6920216 100644
--- a/tox.ini
+++ b/tox.ini
@@ -36,7 +36,7 @@ commands = flake8 pgmigrate.py setup.py
 deps = flake8
        flake8-mock
        flake8-string-format
-       flake8-isort
+       flake8-isort>=4.0.0
        flake8-commas
        flake8-quotes
        flake8-copyright