diff --git a/Dockerfile b/Dockerfile
index 02aa0f0d737..28c4affb527 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,7 @@
 # https://github.com/letsencrypt/letsencrypt/pull/431#issuecomment-103659297
 # it is more likely developers will already have ubuntu:trusty rather
 # than e.g. debian:jessie and image size differences are negligible
-FROM ubuntu:trusty
+FROM ubuntu:trusty-20190515
 MAINTAINER Jakub Warmuz <jakub@warmuz.org>
 MAINTAINER William Budington <bill@eff.org>