unable to extend model in codeigniter 2

[eluser]ixxalnxxi[/eluser]
error: Fatal error: Class 'MY_Model' not found in /home/tipu/Dropbox/dev/workspace/project_root/application/models/tournament_model.php on line 3

tournament_model class declaration:
class Tournament_model extends MY_Model

MY_Model.php is located at project_root/application/core/MY_Model.php

the class declaration is:

class MY_model extends CI_Model

any ideas?

edit: these models work when extending CI_Model, i just can't extend from my own child model class, MY_Model.

[eluser]InsiteFX[/eluser]

Code:

class MY_model extends CI_Model
// should be
class MY_Model extends CI_Model

InsiteFX