NodeJS - MongooseJS schema error that i cant figure out

Maybe a second set of eyes can see what is wrong with my schema

var UserSchema = new Schema({
        name: 
                {
                        first : {type: String}
                    ,   last : {type : String}
                }
    ,   password: {type: String}
    ,   username: {type: String}
    , role: RoleSchema
  , created_at  : {type : Date, default : Date.now}
  , modified_at  : {type : Date, default : Date.now}
})

var RoleSchema = {
        type: [String]
    ,   study_type: [String]
}

mongoose.model('User', UserSchema)

The Error:

TypeError: Invalid value for schema path `role`