Doesn't support inheritance in the same namespace

Hi,

Does this sample supports classes inheritance in the same namespace?
For example, I've copied this project to my computer and:
1. added a class ADataService which inherits from DataService. both are in the app.core namespace
2. run the gulp task 'optimize'
3. I see that the index.html references first the ADataService .js...and in the browser I get an error the cannot read property 'prototype' of undefined in the ADataService class definition

note that the page loads successfully.