diff --git a/virtualbox/Dockerfile b/virtualbox/Dockerfile
index 64c753f..15b1df0 100644
--- a/virtualbox/Dockerfile
+++ b/virtualbox/Dockerfile
@@ -32,20 +32,19 @@
 FROM debian:sid
 MAINTAINER Jessie Frazelle <jess@linux.com>
 
-RUN apt-get update && apt-get install -y \
-	ca-certificates \
-	curl \
-	gnupg \
-	--no-install-recommends \
+RUN buildDeps=' \
+		ca-certificates \
+		curl \
+		gnupg \
+	' \
+	&& set -x \
+	&& apt-get update && apt-get install -y $buildDeps --no-install-recommends \
+	&& rm -rf /var/lib/apt/lists/* \
 	&& curl -sSL https://www.virtualbox.org/download/oracle_vbox_2016.asc | apt-key add - \
 	&& echo "deb http://download.virtualbox.org/virtualbox/debian stretch contrib" >> /etc/apt/sources.list.d/virtualbox.list \
 	&& apt-get update && apt-get install -y \
 	virtualbox-5.0 \
 	--no-install-recommends \
-	&& apt-get purge -y --auto-remove \
-	ca-certificates \
-	curl \
-	gnupg \
-	&& rm -rf /var/lib/apt/lists/*
+	&& apt-get purge -y --auto-remove $buildDeps
 
 ENTRYPOINT	[ "/usr/bin/virtualbox" ]