diff --git a/tox.ini b/tox.ini
index fc09572..6e6d267 100644
--- a/tox.ini
+++ b/tox.ini
@@ -42,7 +42,7 @@ setenv =
 deps =
     mypy == 0.971
     types-pkg_resources
-    types-PyYAML
+    types-PyYAML == 6.0.12.12
     types-docopt
 commands =
     mypy gdtoolkit/ tests/ --config-file tox.ini