diff --git a/requirements.txt b/requirements.txt
old mode 100755
new mode 100644
index a0641b2e..a74f33d2
--- a/requirements.txt
+++ b/requirements.txt
@@ -48,7 +48,7 @@ Twisted==17.9.0
 txaioetcd==0.3.0
 urllib3==1.22
 pyang==1.7.3
-lxml==3.6.4
+lxml==4.9.1
 nosexcover==1.0.11
 zmq==0.0.0
 pyzmq==16.0.3