Inherit custom operator= from template base class

Question

I have a template base class that implements void operator=(T value). Then I have a derived template class which should just inherit that operator, but this doesn't work. (See compile error in the code comment.) When I just rename the operator to void operator+=(T value) it works so there must be some magic going on with the assignment operator.

#include <iostream>

template<typename T>
class A
{
public:
    void operator=(T value) {
        _value = value;
    }

    T value() {
        return _value;
    }

    void print() {
        std::cout << "A: " << value() << std::endl;
    }

private:
    T _value;
};

template<typename T>
class B : public A<T>
{
public:
    void print() {
        std::cout << "B: " << this->value() << std::endl;  // Why is "this->" needed?
    }
};

int main(int, char**)
{
    // Works just fine
    A<int> a;
    a = 4;
    a.print();

    // Doesn't compile
    B<int> b;
    b = 5;      // error: no match for ‘operator=’ (operand types are ‘B<int>’ and ‘int’)
    b.print();

    return 0;
}

Edit: I know there are a lot answered questions like this. But they all use the operator= with the same signature that the default generated assignment operator would have. But I don't have this signature and so the explanations there do not directly apply for me.