configuration-as-code-plugin: ConfiguratorException: No configurator for root element

I have the following error when trying to test the sample proposed in the How to create initial seed job section of the README.

Log

jenkins_1  | Jul 03, 2018 8:34:51 PM org.jenkinsci.plugins.casc.BaseConfigurator configure
jenkins_1  | INFO: Setting hudson.model.Hudson@3cab0202.systemMessage = Simple seed job example
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.InitReactorRunner$1 onTaskFailed
jenkins_1  | SEVERE: Failed ConfigurationAsCode.init
jenkins_1  | java.lang.Error: java.lang.reflect.InvocationTargetException
jenkins_1  | 	at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:110)
jenkins_1  | 	at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:175)
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
jenkins_1  | 	at jenkins.model.Jenkins$5.runTask(Jenkins.java:1065)
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
jenkins_1  | 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
jenkins_1  | 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
jenkins_1  | 	at java.lang.Thread.run(Thread.java:748)
jenkins_1  | Caused by: java.lang.reflect.InvocationTargetException
jenkins_1  | 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
jenkins_1  | 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
jenkins_1  | 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
jenkins_1  | 	at java.lang.reflect.Method.invoke(Method.java:498)
jenkins_1  | 	at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:104)
jenkins_1  | 	... 8 more
jenkins_1  | Caused by: org.jenkinsci.plugins.casc.ConfiguratorException: No configurator for root element <jobs>
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:427)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:351)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configure(ConfigurationAsCode.java:324)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configure(ConfigurationAsCode.java:178)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.init(ConfigurationAsCode.java:147)
jenkins_1  | 	... 13 more
jenkins_1  | 
jenkins_1  | Jul 03, 2018 8:34:51 PM hudson.util.BootFailure publish
jenkins_1  | SEVERE: Failed to initialize Jenkins
jenkins_1  | hudson.util.HudsonFailedToLoad: org.jvnet.hudson.reactor.ReactorException: java.lang.Error: java.lang.reflect.InvocationTargetException
jenkins_1  | 	at hudson.WebAppMain$3.run(WebAppMain.java:250)
jenkins_1  | Caused by: org.jvnet.hudson.reactor.ReactorException: java.lang.Error: java.lang.reflect.InvocationTargetException
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:269)
jenkins_1  | 	at jenkins.InitReactorRunner.run(InitReactorRunner.java:47)
jenkins_1  | 	at jenkins.model.Jenkins.executeReactor(Jenkins.java:1099)
jenkins_1  | 	at jenkins.model.Jenkins.<init>(Jenkins.java:904)
jenkins_1  | 	at hudson.model.Hudson.<init>(Hudson.java:86)
jenkins_1  | 	at hudson.model.Hudson.<init>(Hudson.java:82)
jenkins_1  | 	at hudson.WebAppMain$3.run(WebAppMain.java:233)
jenkins_1  | Caused by: java.lang.Error: java.lang.reflect.InvocationTargetException
jenkins_1  | 	at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:110)
jenkins_1  | 	at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:175)
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
jenkins_1  | 	at jenkins.model.Jenkins$5.runTask(Jenkins.java:1065)
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
jenkins_1  | 	at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
jenkins_1  | 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
jenkins_1  | 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
jenkins_1  | 	at java.lang.Thread.run(Thread.java:748)
jenkins_1  | Caused by: java.lang.reflect.InvocationTargetException
jenkins_1  | 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
jenkins_1  | 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
jenkins_1  | 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
jenkins_1  | 	at java.lang.reflect.Method.invoke(Method.java:498)
jenkins_1  | 	at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:104)
jenkins_1  | 	... 8 more
jenkins_1  | Caused by: org.jenkinsci.plugins.casc.ConfiguratorException: No configurator for root element <jobs>
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:427)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configureWith(ConfigurationAsCode.java:351)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configure(ConfigurationAsCode.java:324)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.configure(ConfigurationAsCode.java:178)
jenkins_1  | 	at org.jenkinsci.plugins.casc.ConfigurationAsCode.init(ConfigurationAsCode.java:147)
jenkins_1  | 	... 13 more
jenkins_1  | 
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins cleanUp
jenkins_1  | INFO: Stopping Jenkins
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins$19 onAttained
jenkins_1  | INFO: Started termination
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins$19 onAttained
jenkins_1  | INFO: Completed termination
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins _cleanUpDisconnectComputers
jenkins_1  | INFO: Starting node disconnection
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins _cleanUpShutdownPluginManager
jenkins_1  | INFO: Stopping plugin manager
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins _cleanUpPersistQueue
jenkins_1  | INFO: Persisting build queue
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins _cleanUpAwaitDisconnects
jenkins_1  | INFO: Waiting for node disconnection completion
jenkins_1  | Jul 03, 2018 8:34:51 PM jenkins.model.Jenkins cleanUp
jenkins_1  | INFO: Jenkins stopped

Environment

• Tests done in Docker
• Jenkins version : 2.89.2
• Jenkins CasC version : 0.9-alpha

Steps to reproduce

# Create docker-compose.yml
cat << EOF > docker-compose.yml
version: "3"
 
services:
  jenkins:
    image: jenkins/jenkins:lts
    ports:
      - 8080:8080
    environment: 
     - CASC_JENKINS_CONFIG=/var/jenkins_home/casc/jenkins.yml
    volumes: 
      - ./data:/var/jenkins_home
EOF

# Create jenkins.yml from the documentation sample
cat << EOF > ./data/casc/jenkins.yml
jenkins:
  systemMessage: "Simple seed job example"
jobs:
  - >
    multibranchPipelineJob('configuration-as-code') {
      branchSources {
        git {
          remote('https://github.com/jenkinsci/configuration-as-code-plugin.git')
          }
      }
    }
EOF

# Launch Jenkins
docker-compose up -d