diff --git a/test/Dockerfile b/test/Dockerfile
index 5a2b29e19ccca91a161a37b4d4b6a3ca9c0ea5e0..0555f1f6da4cf294cf41c554e96545e530dc68f4 100644
--- a/test/Dockerfile
+++ b/test/Dockerfile
@@ -4,7 +4,7 @@ FROM debian:${DEBIAN_VERSION}
 RUN sed -i -e '/^Templates:/aFrontend: noninteractive' /etc/debconf.conf
 
 ARG http_proxy
-RUN [ -n "$http_proxy" ] && echo 'Acquire::http::Proxy "'$http_proxy'";' >/etc/apt/apt.conf.d/80proxies
+RUN if [ -n "$http_proxy" ] ; then echo 'Acquire::http::Proxy "'$http_proxy'";' >/etc/apt/apt.conf.d/80proxies ; fi
 RUN echo 'Acquire::https::Proxy "DIRECT";' >>/etc/apt/apt.conf.d/80proxies
 
 RUN apt-get update -yqq