diff --git a/requirements.txt b/requirements.txt
index f01f2cb..3ed8b6c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,5 @@
+#TODO: Remove lxml once the upstream issue https://github.com/vfaronov/httpolice/issues/5 with HTTpolice is fixed.
+lxml==3.6.0
 coala_bears~=0.12.0.dev20170722110839
 coala_utils~=0.4
 gemfileparser~=0.6.2