overrides – Overide a class doesn’t work for his child?

I want to override this class : ‘MagentoCheckoutBlockCartItemRenderer’
This class has a child like : ‘MagentoConfigurableProductBlockCartItemRenderer’

So i use <preference for="MagentoCheckoutBlockCartItemRenderer" type="CustomCheckoutBlockCartItemRenderer" />

It’s works only when i use the parent class ( CartItemRenderer ). but when i instantiate the child i can’t use my custom function.
Is there something else to do ?
I have to override all the child class ?