diff --git a/CHANGES.rst b/CHANGES.rst
index 3170027..ade20d4 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -14,6 +14,8 @@ Changelog
 
 - fixed several errors due to changed behavior in Python 3
 
+- update `isort` to version 5.
+
 
 4.0.2 (2019-02-17)
 ------------------
diff --git a/tox.ini b/tox.ini
index bc70b97..dd1320a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -43,11 +43,10 @@ deps =
     flake8-debugger
     flake8-deprecated
     flake8-todo
-    flake8-isort
     mccabe
     flake8-blind-except
     flake8-commas
 commands =
-    - isort --check-only {toxinidir}/src setup.py
+    isort {toxinidir}/src setup.py
     flake8 --doctests src setup.py {posargs}
     isort --version