Ensure abstract bass class is a shared_ptr

I have an abstract base class:

struct Base : std::enable_shared_from_this<Base> 
{
    virtual ~Base() = default;
    virtual void foo() = 0;

    void bar() {
        baz(shared_from_this());
    }
};

The only valid use case for Base is to live in a shared_ptr - bar is an important method. How can I ensure that the following is impossible:

struct BadDerived : Base {
    void foo() override { ... }
};

BadDerived bd;
bd.bar();