diff --git a/requirements_dev.txt b/requirements_dev.txt
index 0724f23..7ca16a5 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -1,5 +1,5 @@
 flake8
-tox
+tox==4.3.5
 coverage
 Sphinx
 PyYAML