diff --git a/circle.yml b/circle.yml
index 455718c..82a0a08 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,7 +1,9 @@
 machine:
   pre:
-    # install docker 1.9.1
+    # install docker 1.9.1 with some CircleCI suggestions:
+    # https://discuss.circleci.com/t/how-use-a-different-docker-version/298/8
     - sudo curl -L -o /usr/bin/docker 'https://s3-external-1.amazonaws.com/circle-downloads/docker-1.9.1-circleci'; sudo chmod 0755 /usr/bin/docker; true
+    - sudo sed -i -e 's/ --userland-proxy=false//' /etc/default/docker
   services:
     - docker
 
diff --git a/test/docker.bats b/test/docker.bats
index 1de063d..f705432 100644
--- a/test/docker.bats
+++ b/test/docker.bats
@@ -105,10 +105,10 @@ function assert_nginxproxy_behaves {
 
 	# Querying the proxy with Host header → 200
 	run curl_container $container /data --header "Host: web1.bats"
-	assert_output "answer from port 81"
+	assert_output -l 0 "answer from port 81"
 
 	run curl_container $container /data --header "Host: web2.bats"
-	assert_output "answer from port 82"
+	assert_output -l 0 "answer from port 82"
 	
 	# Querying the proxy with unknown Host header → 503
 	run curl_container $container /data --header "Host: webFOO.bats" --head
diff --git a/test/multiple-hosts.bats b/test/multiple-hosts.bats
index 695aec1..40c3a39 100644
--- a/test/multiple-hosts.bats
+++ b/test/multiple-hosts.bats
@@ -32,9 +32,9 @@ function setup {
 
 	# THEN
 	run curl_container $SUT_CONTAINER /data --header 'Host: multiple-hosts-1-A.bats'
-	assert_output "answer from port 80"
+	assert_output -l 0 "answer from port 80"
 
 	# THEN
 	run curl_container $SUT_CONTAINER /data --header 'Host: multiple-hosts-1-B.bats'
-	assert_output "answer from port 80"
+	assert_output -l 0 "answer from port 80"
 }
diff --git a/test/multiple-ports.bats b/test/multiple-ports.bats
index a520571..8e0d9ae 100644
--- a/test/multiple-ports.bats
+++ b/test/multiple-ports.bats
@@ -52,6 +52,6 @@ function setup {
 function assert_response_is_from_port {
 	local -r port=$1
 	run curl_container $SUT_CONTAINER /data --header "Host: web.bats"
-	assert_output "answer from port $port"
+	assert_output -l 0 "answer from port $port"
 }
 
diff --git a/test/test_helpers.bash b/test/test_helpers.bash
index 15d82bd..73f1105 100644
--- a/test/test_helpers.bash
+++ b/test/test_helpers.bash
@@ -129,6 +129,6 @@ function prepare_web_container {
 	IFS=$' \t\n' # See https://github.com/sstephenson/bats/issues/89
 	for port in $ports; do
 		run retry 5 1s docker run --rm appropriate/curl --silent --fail http://$(docker_ip $container_name):$port/data
-		assert_output "answer from port $port"
+		assert_output -l 0 "answer from port $port"
 	done
 }