Using Postgres with Grails

Has anyone gotten Grails working with Postgres? I have used this tutorial and everything seems to make sense and be correct to me. However when I 'grails run-app' I get this error

Cannot create JDBC driver of class 'org.postgresql.Driver' for connect URL 'jdbc:postgres://10.0.0.21/tribes'
java.sql.SQLException: No suitable driver

My DataSource file is

dataSource {
    pooled = true
    driverClassName = "org.postgresql.Driver"
    dialect = org.hibernate.dialect.PostgreSQLDialect
}
hibernate {
    cache.use_second_level_cache=true
    cache.use_query_cache=true
    cache.provider_class='com.opensymphony.oscache.hibernate.OSCacheProvider'
}
// environment specific settings
environments {
    development {
        dataSource {
            dbCreate = "update"
            url = "jdbc:postgres://10.0.0.21:5432/tribes"
            username = "grails"
            password = "grails"
        }   
    }   
    test {
        dataSource {
            dbCreate = "update"
            url = "jdbc:postgres://10.0.0.21:5432/tribes"
            username = "grails"
            password = "grails"
        }   
    }   
    production {
        dataSource {
            dbCreate = "update"
            url = "jdbc:postgres://10.0.0.21:5432/tribes"
            username = "grails"
            password = "grails"
        }   
    }   
}