Extending the default model

[eluser]taewoo[/eluser]
I have a similar issue.
I am creating an abstract class that extends the CI model. My sub-models extend this abstract model (inheriting the methods) with different table name via the constructor

Code:

super('tableName')

PHP is complaining that this generic, abstract model cannot be found (even though it's in the same directory) when a controller tries to load the extended sub-model. Is this a path issue or do I need to go wiredesignz method?