diff --git a/tox.ini b/tox.ini
index 9f1586c..62995f6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@ logstash_async_modules = logstash_async tests
 [testenv]
 deps =
     flake8
-    isort
+    isort<5
     pylint
 commands =
     # linting and code analysis
@@ -29,7 +29,7 @@ commands =
 # for Python 2.7.
 deps =
     flake8
-    isort
+    isort<5
 commands =
     # linting and code analysis
     {envbindir}/flake8 {[tox]logstash_async_modules}