diff --git a/ubuntu-openjdk-7/Dockerfile b/ubuntu-openjdk-7/Dockerfile
index 4088b141..5758ce64 100644
--- a/ubuntu-openjdk-7/Dockerfile
+++ b/ubuntu-openjdk-7/Dockerfile
@@ -2,7 +2,7 @@ FROM ubuntu:trusty
 
 MAINTAINER itzg
 
-ENV BUILT_ON 20140517
+ENV APT_GET_UPDATE 2014-07-19
 
 RUN apt-get update
 RUN apt-get install -y openjdk-7-jre-headless