diff --git a/tests/unit/requirements.txt b/tests/unit/requirements.txt
index 3cf288fef9..237baff9ae 100644
--- a/tests/unit/requirements.txt
+++ b/tests/unit/requirements.txt
@@ -17,7 +17,8 @@ PyGithub
 httmock
 
 # requirement for maven_artifact module
-lxml
+lxml < 4.3.0 ; python_version < '2.7' # lxml 4.3.0 and later require python 2.7 or later
+lxml ; python_version >= '2.7'
 semantic_version
 
 # requirement for datadog_downtime module