Google Schema Violation Error with scope parameter

Question

I have a scenario here that I am creating an application which I need to get into connection with Google API Server. Upon Authorization request I encounter an error that says The problem is an XML schema violation error. The line question (no. 47 of the Mule configuration file) is this:

<oauth2:authorization-request 
    authorizationUrl="https://accounts.google.com/o/oauth2/auth" 
    localAuthorizationUrl="https://localhost:8082/authorization" 
    scope="https://www.googleapis.com/auth/admin.directory.user"
/>

Mule's OAuth2 schema doesn't seem to allow a scope parameter to be included in an authorization-request element. Yet, when removed,I get a response of:

{
  "error" : "invalid_request",
  "error_description" : "Missing required parameter: scope"
}

I've carefully followed and implemented the instructions in the Google documents but still failures appears to my end. Looking forward to whatever suggestions.