MongoDB plugin in Grails and Criteria queries

GrailsMongoDBTest.groovy

/* ASSUME FOLLOWING OBJECT MODEL

class Address {
    String street
    String city
}

class Role {
    boolean admin
    String type
    String description
}

class User {
    static embedded = [ 'address' ]

    String first
    String last
    Role role
    Address address
}

class Face {
    User user
    Integer x
    Integer y
    Integer w
    Integer h
    String description
}

class Photo {
    static embedded = [ 'faces' ]

    User user
    String description
    List<String> tags
    List<Face> faces
}

class Gallery {
    static embedded = [ 'photos' ]

    User user
    String name
    String description
    List<Photo> photos
}
*/

// THIS WORKS AND PRODUCES MONGODB QUERY: query: { photos: { $elemMatch: { faces: { $elemMatch: { x: 1 } } } } }
def criteria = Gallery.createCriteria()
criteria.list {
   photos {
       faces {
           eq('x', 1)
       }
   }
}

// THIS FAILS PRODUCING QUERY (NOTE MISSING elemMatch): query: { photos: { $elemMatch: { faces: { $elemMatch: {} } } } }
Gallery.findAll {
    photos {
        faces {
            eq('x', 1)
        }
    }
}

// THIS ALSO FAILS PRODUCING SAME QUERY: query: { photos: { $elemMatch: { faces: { $elemMatch: {} } } } }
Gallery.where {
    photos {
        faces {
            eq('x', 1)
        }
    }
}.list()