diff --git a/tests/docker/docker.py b/tests/docker/docker.py
index 9fd32ab5faf6beebc83781276f6bc4861043cbbc..8747f6a4404370239273b99bcdbbf7bdde4638aa 100755
--- a/tests/docker/docker.py
+++ b/tests/docker/docker.py
@@ -28,6 +28,9 @@ from shutil import copy, rmtree
 from pwd import getpwuid
 
 
+FILTERED_ENV_NAMES = ['ftp_proxy', 'http_proxy', 'https_proxy']
+
+
 DEVNULL = open(os.devnull, 'wb')
 
 
@@ -272,6 +275,9 @@ class BuildCommand(SubCommand):
                 _copy_binary_with_libs(args.include_executable,
                                        docker_dir)
 
+            argv += ["--build-arg=" + k.lower() + "=" + v
+                        for k, v in os.environ.iteritems()
+                        if k.lower() in FILTERED_ENV_NAMES]
             dkr.build_image(tag, docker_dir, dockerfile,
                             quiet=args.quiet, user=args.user, argv=argv)
 
diff --git a/tests/docker/dockerfiles/debian-s390x-cross.docker b/tests/docker/dockerfiles/debian-s390x-cross.docker
index bbb21ed088301b466442f5aa29041eb61cb6b812..3a687feda0cba0085f9142702f339d0cd28e5d91 100644
--- a/tests/docker/dockerfiles/debian-s390x-cross.docker
+++ b/tests/docker/dockerfiles/debian-s390x-cross.docker
@@ -13,8 +13,8 @@ RUN cat /etc/apt/sources.list | sed "s/deb/deb-src/" >> /etc/apt/sources.list
 RUN dpkg --add-architecture s390x
 
 # Grab the updated list of packages
-RUN apt update
-RUN apt dist-upgrade -yy
+RUN apt update && apt dist-upgrade -yy
+RUN apt install -yy build-essential clang
 RUN apt-get build-dep -yy -a s390x qemu || apt-get -f install
 RUN apt install -yy gcc-multilib-s390x-linux-gnu binutils-multiarch