diff --git a/requirements/common.txt b/requirements/common.txt
index 50fb18388b..48726d5f83 100644
--- a/requirements/common.txt
+++ b/requirements/common.txt
@@ -181,3 +181,6 @@ pyldap==2.4.37
 
 # Install Python Social Auth
 social-auth-app-django==1.2.0
+
+# Needed for messages' rendered content parsing in push notifications.
+lxml==4.0.0
diff --git a/requirements/dev_lock.txt b/requirements/dev_lock.txt
index f69348002a..d11138ed89 100644
--- a/requirements/dev_lock.txt
+++ b/requirements/dev_lock.txt
@@ -72,7 +72,7 @@ ipython==6.2.0
 jedi==0.10.2              # via ipython
 jinja2==2.9.6
 jmespath==0.9.3           # via boto3, botocore
-lxml==3.8.0               # via parsel, premailer, scrapy
+lxml==4.0.0
 markdown-include==0.5.1
 markdown==2.6.9           # via markdown-include
 markupsafe==1.0
diff --git a/requirements/prod_lock.txt b/requirements/prod_lock.txt
index 316a16689e..82cab34646 100644
--- a/requirements/prod_lock.txt
+++ b/requirements/prod_lock.txt
@@ -51,7 +51,7 @@ ipython-genutils==0.2.0   # via traitlets
 ipython==6.2.0
 jedi==0.10.2              # via ipython
 jinja2==2.9.6
-lxml==3.8.0               # via premailer
+lxml==4.0.0
 markdown-include==0.5.1
 markdown==2.6.9           # via markdown-include
 markupsafe==1.0
diff --git a/version.py b/version.py
index 21c8d34995..1622b63035 100644
--- a/version.py
+++ b/version.py
@@ -1,2 +1,2 @@
 ZULIP_VERSION = "1.6.0+git"
-PROVISION_VERSION = '10.3'
+PROVISION_VERSION = '10.4'