diff --git a/pyproject.toml b/pyproject.toml
index 8f1aefb..04a24b3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,7 +25,7 @@ docs = ["Sphinx", "sphinx-rtd-theme"]
 bandit = "^1.7.0"
 importlib-metadata = "<7" # Workaround for https://github.com/PyCQA/bandit/issues/951
 isort = "^5.7.0" 
-lxml = "^5.2.2" 
+lxml = ">=5.2.2,<7.0.0" 
 mypy = "^1.1"
 pytest = "^7.0.0" 
 pytest-cov = "^4.0.0"