sentinl: email_html action raises an error

Using the same watcher, I define 2 actions : one email and one email_html with nearly the same configuration. I receive well the email one, but not the email_html one.

When looking at logs, I can see this error log : {"type":"log","@timestamp":"2017-01-17T14:50:00Z","tags":["error","Sentinl"],"pid":11701,"message":"An error occurred while executing the watch: TypeError: Cannot read property 'active' of undefined"}

Is there a special entry to activate in kibana.yml ?

I use Kibana 4.6.3.

Here’s my kibana.yml sentinl configuration :

sentinl:
  es:
    timefield: '@timestamp'
    default_index: watcher
    type: watch
    alarm_index: watcher_alarms
  sentinl:
    history: 20
    results: 50
  settings:
    email:
      active: true
      host: localhost
      ssl: false
    report:
      active: true
      tmp_path: /tmp/

Here’s my watcher :

{
  "_index": "watcher",
  "_type": "watch",
  "_id": "test_watch_fba",
  "_score": 1,
  "_source": {
    "disable": false,
    "trigger": {
      "schedule": {
        "later": "every 1 day at 2:27 pm"
      }
    },
    "input": {
      "search": {
        "request": {
          "index": "<logstash-{now-1d/d}>,<logstash-{now-2d/d}>",
          "body": {
            "size": 0,
            "query": {
              "filtered": {
                "query": {
                  "query_string": {
                    "query": "*"
                  }
                },
                "filter": {
                  "range": {
                    "@timestamp": {
                      "from": "now-1d/d",
                      "to": "now-1d/d",
                      "time_zone": "Europe/Paris"
                    }
                  }
                }
              }
            }
          }
        }
      }
    },
    "condition": {
      "script": {
        "script": "payload.hits.total > 0"
      }
    },
    "transform": {},
    "actions": {
      "send_email_fba": {
        "email": {
          "to": "fba@mycompany.com",
          "from": "kibana@mycompany.com",
          "subject": "SENTINL TEST NOT HTML",
          "priority": "high",
          "body": "Total Hits: {{ payload.hits.total }}",
          "stateless": false
        }
      },
      "send_email_html_fba": {
        "email_html": {
          "to": "fba@mycompany.com",
          "from": "kibana@mycompany.com",
          "subject": "SENTINL TEST HTML",
          "priority": "high",
          "body": "Total Hits: {{ payload.hits.total }}",
          "html": "<p>Total Hits: {{ payload.hits.total }}</p>",
          "stateless": false
        }
      }
    }
  }
}