diff --git a/engine/examples/running_riak_service.Dockerfile b/engine/examples/running_riak_service.Dockerfile
index 7aeaca3..867623d 100644
--- a/engine/examples/running_riak_service.Dockerfile
+++ b/engine/examples/running_riak_service.Dockerfile
@@ -3,7 +3,7 @@
 # VERSION       0.1.1
 
 # Use the Ubuntu parent image provided by dotCloud
-FROM ubuntu:trusty
+FROM ubuntu:trusty-20190515
 
 # Install Riak repository before we do apt-get update, so that update happens
 # in a single step