diff --git a/requirements.txt b/requirements.txt
index 1f58975..7251548 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@ ase==3.13.0
 numpy==1.9.0
 Cython==0.25.2
 Pmw==2.0.1
-lxml==3.7.3
+lxml==4.6.3
 matplotlib==2.0.2
 mpi4py==2.0.0
 np==0.2.0