diff --git a/lower-constraints.txt b/lower-constraints.txt
index 6706c9a347..4d013afb3d 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -34,7 +34,7 @@ Jinja2==2.10
 keystoneauth1==3.4.0
 keystonemiddleware==4.17.0
 linecache2==1.0.0
-lxml==3.4.1
+lxml==4.2.3
 MarkupSafe==1.0
 mock==3.0
 monotonic==1.4
diff --git a/requirements.txt b/requirements.txt
index 892fd5f79d..97d440981e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,7 +5,7 @@
 eventlet>=0.25.0,!=0.34.3               # MIT
 greenlet>=0.3.2
 PasteDeploy>=2.0.0
-lxml>=3.4.1
+lxml>=4.2.3
 requests>=2.14.2                        # Apache-2.0
 six>=1.10.0
 xattr>=0.4;sys_platform!='win32'        # MIT