Error when uploading updated application manifest

I'm trying to set up AAD authentication for a WCF service hosted on an Azure web site, which will be called by a client application. I've gone through the steps to set up the client in AAD, and downloaded and edited the manifest for the web site as described here: http://msdn.microsoft.com/en-us/library/azure/dn132599.aspx#BKMK_Exposing. However, when I try to upload the updated manifest file, I receive the error "Failed to upload manifest for [website]." Clicking "Details" gives me "ParameterValidationException=Invalid parameters provided; BadRequestException=Property value cannot be deleted unless it is disabled first.;"

The only change I've made to the manifest file is to supply the correct GUID for my client application at oauth2Permissions.id.

The complete oauth2Permissions section (with identifying details removed) is:

"oauth2Permissions": [
    {
      "adminConsentDescription": "Allow the application to access [website] on behalf of the signed-in user.",
      "adminConsentDisplayName": "Access [website]",
      "id": "[client GUID]",
      "isEnabled": true,
      "origin": "Application",
      "type": "User",
      "userConsentDescription": "Allow the application to access [website] on your behalf.",
      "userConsentDisplayName": "Access [website]",
      "value": "user_impersonation"
    }
  ],

Any suggestions?