Change Azure AD B2C User Password with Graph API

I'm trying to use the Sample Graph API app to change a user's password but I'm getting:

Error Calling the Graph API Response:

{
  "odata.error": {
    "code": "Authorization_RequestDenied",
    "message": {
      "lang": "en",
      "value": "Insufficient privileges to complete the operation."
    }
  }
}

Graph API Request:

PATCH /mytenant.onmicrosoft.com/users/some-guid?api-version=1.6 HTTP/1.1
client-request-id: ffd564d3-d716-480f-a66c-07b02b0e32ab
date-time-utc: 2017.08.10 03:04 PM

JSON File

{
    "passwordProfile": {
        "password": "Somepassword1$",
        "forceChangePasswordNextLogin": false
    }
}

I've tested updating the user's displayName and that works fine.

{
    "displayName": "Joe Consumer"
}

AD Application Permissions

I've configured my app permissions as described here.