SERVICE_CHECK_HTTP not passing in Headers environment variable

[smarshal-Quest]

• What version of docker are you running?
  Docker version 17.03.2-ce, build f5ec1e2
  docker-compose version 1.6.2, build 4d72027
• What version of registrator are you running?
  v7
• Did you build a custom version of registrator? If so, what is that image?
  no (gliderlabs/registrator:v7)
• What is the exact command you are running registrator with?
  registrator:
  image: gliderlabs/registrator:v7
  command: -ip="${BIND_ADDRESS}" consul://localhost:8500
  network_mode: host
  restart: always
  depends_on:
  - consul
  volumes:
  - /var/run/docker.sock:/tmp/docker.sock
• What is the exact command you are running your container with?
• A log capture of all the docker events before, during, and after the issue.
• If relevant, Dockerfile for application that is having issues.

Description of the problem:
SERVICE_CHECK_HTTP with
SERVICE_CHECK_HEADER .

registrator is ignoring the header env when bringing up the container. the service check is being registered, but with headers null,
(https://www.consul.io/api/agent/check.html)

How reproducible:

running with docker compose
environment:
"SERVICE_9200_NAME=es-http"
- 'SERVICE_9200_CHECK_HEADER={"Authorization": ["Basic "]}'
- "SERVICE_9200_CHECK_HTTP=/_cluster/health"
- "SERVICE_9200_CHECK_INTERVAL=15s"
- "SERVICE_9200_CHECK_TIMEOUT=3s"
- 'SERVICE_9200_TAGS=LISTEN=9200/http'

Steps to Reproduce:

Actual Results:
cat consul/data/checks/3f365d12ffa259886d19020ee38f94f8 | jq -c
{"Check":{"Node":"swarm-agentpool-sm01sboxwestus2000003","CheckID":"service:swarm-agentpool-sm01sboxwestus2000003:es-master:9200","Name":"Service 'es-http' check","Status":"critical","Notes":"","Output":"","ServiceID":"swarm-agentpool-sm01sboxwestus2000003:es-master:9200","ServiceName":"es-http","ServiceTags":["LISTEN=9200/http"],"Definition":{},"CreateIndex":0,"ModifyIndex":0},"ChkType":{"CheckID":"","Name":"","Status":"","Notes":"","ScriptArgs":null,"HTTP":"http://10.0.0.7:32782/_cluster/health","Header":null,"Method":"","TCP":"","Interval":15000000000,"AliasNode":"","AliasService":"","DockerContainerID":"","Shell":"","GRPC":"","GRPCUseTLS":false,"TLSSkipVerify":false,"Timeout":3000000000,"TTL":0,"DeregisterCriticalServiceAfter":0},"Token":""}

Expected Results:
cat consul/data/checks/3f365d12ffa259886d19020ee38f94f8 | jq -c
{"Check":{"Node":"swarm-agentpool-sm01sboxwestus2000003","CheckID":"service:swarm-agentpool-sm01sboxwestus2000003:es-master:9200","Name":"Service 'es-http' check","Status":"critical","Notes":"","Output":"","ServiceID":"swarm-agentpool-sm01sboxwestus2000003:es-master:9200","ServiceName":"es-http","ServiceTags":["LISTEN=9200/http"],"Definition":{},"CreateIndex":0,"ModifyIndex":0},"ChkType":{"CheckID":"","Name":"","Status":"","Notes":"","ScriptArgs":null,"HTTP":"http://10.0.0.7:32782/_cluster/health","Header":{"Authorization": ["Basic "]},"Method":"","TCP":"","Interval":15000000000,"AliasNode":"","AliasService":"","DockerContainerID":"","Shell":"","GRPC":"","GRPCUseTLS":false,"TLSSkipVerify":false,"Timeout":3000000000,"TTL":0,"DeregisterCriticalServiceAfter":0},"Token":""}

Additional info: