Generalization of class in generic function creates object code for base class?

class A {
protected:
    int fooA;
    A() : fooA(0) {}
};

class B {};

template<typename T>
class C : public A {
public:
    using A::A;

    void fooF(const T element) {
        element.fooA = 1;
    }
};

class D : public C<B>, public B {
    using C::C;
};

int main() {

    D d1;
    D d2;

    d1.fooF(d2);

    return 0;
}

error: ‘const class B’ has no member named ‘fooA’ element.fooA = 1;

It seems like when T is particulariced into B, it transforms d2 into its parent class (B), what can I do to avoid that? (I need to do it that way so i can't change the number of classes either its inheritances). Thanks.