diff --git a/tox.ini b/tox.ini
index f25a59b..acbe911 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@ deps=
     pylint
     semver
     pydocstyle
-    isort
+    isort<5
 commands=
     pycodestyle libagent
     # isort --skip-glob .tox -c -r libagent