Shadow fields from superclass?

I have a class(class B) which i inject code into:

class A {
public Object obj;

class B extends A {
protected void methodA() {

and now i want to inject code like this:

public Object obj;    
@Inject(method="methodA", at =@At("HEAD"))
    protected void injectMethodA() {
    Object o = this.obj;

But it gives me an exception saying that the shadowed field isn’t in the Mixin class. How can I access the superclass?

Make MixinB extends A, so you will be able to access everything defined in A.