diff --git a/2.4.0/centos/7/Dockerfile b/2.4.0/centos/7/Dockerfile
index ff021f2..0f70c49 100644
--- a/2.4.0/centos/7/Dockerfile
+++ b/2.4.0/centos/7/Dockerfile
@@ -1,11 +1,15 @@
 FROM centos:7
 MAINTAINER Peter Ericson <pdericson@gmail.com>
 
-# https://github.com/Yelp/dumb-init
-RUN curl -fLsS -o /usr/local/bin/dumb-init https://github.com/Yelp/dumb-init/releases/download/v1.0.2/dumb-init_1.0.2_amd64 && chmod +x /usr/local/bin/dumb-init
+ENV CHRONOS_VERSION=2.4.0
+ENV MESOS_VERSION=0.24.1
 
-RUN rpm -i http://repos.mesosphere.io/el/7/noarch/RPMS/mesosphere-el-repo-7-1.noarch.rpm && \
-yum -y install chronos-2.4.0 mesos-0.24.1
+# https://github.com/Yelp/dumb-init
+RUN curl -fLsS -o /usr/local/bin/dumb-init https://github.com/Yelp/dumb-init/releases/download/v1.0.2/dumb-init_1.0.2_amd64 && \
+    chmod +x /usr/local/bin/dumb-init && \
+    rpm -i http://repos.mesosphere.io/el/7/noarch/RPMS/mesosphere-el-repo-7-1.noarch.rpm && \
+    yum -y install "chronos-$CHRONOS_VERSION" "mesos-$MESOS_VERSION" && \
+    yum clean all
 
 COPY entrypoint.sh /