Github plugin 1.9.1

In "Manage Jenkins/Configure System" I have chosen the option "Let Jenkins auto-manage hook URLs" with a username and Oauth token (verification ok). Afterwards I setup in my build job to "Build when a change is pushed to GitHub". The service is added in Github under "Webhooks & Services". Whenever a change is pushed the build job is triggered: nice. But when I just go to "Manage Jenkins/Configure System" and hit the save button (without making any change) the service is being removed in Github under "Webhooks & Services" !?