diff --git a/circle.yml b/circle.yml
index 41a768db..23a67833 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,5 +1,6 @@
 machine:
   environment:
+    MACH_PREFIX: tendermint-test-mach
     GOPATH: /home/ubuntu/.go_workspace
     REPO: $GOPATH/src/github.com/$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME
     DOCKER_VERSION: 1.10.0
diff --git a/test/net/test.sh b/test/net/test.sh
index 02a5bdf0..b5809b26 100644
--- a/test/net/test.sh
+++ b/test/net/test.sh
@@ -6,10 +6,15 @@ VALSETSIZE=4
 BLOCKSIZE=8092
 TX_SIZE=200
 NTXS=$((BLOCKSIZE*4))
-MACH_PREFIX=mach
 RESULTSDIR=results
 CLOUD_PROVIDER=digitalocean
 
+set +u
+if [[ "$MACH_PREFIX" == "" ]]; then
+	MACH_PREFIX=mach
+fi
+set -u
+
 export TMHEAD=`git rev-parse --abbrev-ref HEAD`
 export TM_IMAGE="tendermint/tmbase"