diff --git a/.gitignore b/.gitignore
index 2cefdfb7..4506fcc5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -48,7 +48,7 @@ releases
 .weaver.uptodate
 .weavedns.uptodate
 .weaveexec.uptodate
-weave.tar
+weave.tar.gz
 prog/weaveexec/weave
 prog/weaveexec/weavehosts
 prog/weaveexec/weaveproxy
diff --git a/Makefile b/Makefile
index 1757de4a..7431459e 100644
--- a/Makefile
+++ b/Makefile
@@ -30,7 +30,7 @@ WEAVEEXEC_IMAGE=$(DOCKERHUB_USER)/weaveexec
 
 IMAGES=$(WEAVER_IMAGE) $(WEAVEEXEC_IMAGE)
 
-WEAVE_EXPORT=weave.tar
+WEAVE_EXPORT=weave.tar.gz
 
 WEAVEEXEC_DOCKER_VERSION=1.3.1
 DOCKER_DISTRIB=prog/weaveexec/docker-$(WEAVEEXEC_DOCKER_VERSION).tgz
@@ -105,7 +105,7 @@ $(WEAVEEXEC_UPTODATE): prog/weaveexec/Dockerfile $(DOCKER_DISTRIB) weave $(SIGPR
 	touch $@
 
 $(WEAVE_EXPORT): $(IMAGES_UPTODATE)
-	$(SUDO) docker save $(addsuffix :latest,$(IMAGES)) > $@
+	$(SUDO) docker save $(addsuffix :latest,$(IMAGES)) | gzip > $@
 
 $(DOCKER_DISTRIB):
 	curl -o $(DOCKER_DISTRIB) $(DOCKER_DISTRIB_URL)
diff --git a/site/building.md b/site/building.md
index 2d7b713f..41b0bfe1 100644
--- a/site/building.md
+++ b/site/building.md
@@ -54,7 +54,7 @@ $ make
 
 This will build the weave components and package them into three
 Docker images (`weaveworks/weave`, `weaveworks/weavedns`, and
-`weaveworks/weaveexec`).  These are then exported as `weave.tar`.
+`weaveworks/weaveexec`).  These are then exported as `weave.tar.gz`.
 
 ## Building in a Docker container
 
@@ -167,13 +167,13 @@ you can do so with
 $ vagrant ssh -c 'make -C src/github.com/weaveworks/weave'
 ```
 
-you should then find a `weave.tar` container snapshot tarball in the
+you should then find a `weave.tar.gz` container snapshot tarball in the
 top-level directory. You can use that snapshot with `docker load`
 against a different host, e.g.
 
 ```bash
 $ export DOCKER_HOST=tcp://<HOST:PORT>
-$ docker load < weave.tar
+$ docker load < weave.tar.gz
 ```
 
 You can provide extra Vagrant configuration by putting a file
diff --git a/test/setup.sh b/test/setup.sh
index 11280ce2..9312fc20 100755
--- a/test/setup.sh
+++ b/test/setup.sh
@@ -13,7 +13,7 @@ echo "  prefetch test images"
 
 setup_host() {
     HOST=$1
-    docker_on $HOST load -i ../weave.tar
+    docker_on $HOST load -i ../weave.tar.gz
     DANGLING_IMAGES="$(docker_on $HOST images -q -f dangling=true)"
     [ -n "$DANGLING_IMAGES" ] && docker_on $HOST rmi $DANGLING_IMAGES 1>/dev/null 2>&1 || true
     run_on $HOST mkdir -p bin