Although unique_ptr guaranteed to store nullptr after move, it still is pointing to the object?

I've tested following code with GCC 5.2 (C++11):

#include <iostream>
#include <memory>

struct Foo
{
    Foo()      { std::cout << "Foo::Foo\n";  }
    ~Foo()     { std::cout << "Foo::~Foo\n"; }
    void bar() { std::cout << "Foo::bar\n";  }
};

void f(const Foo &)
{
    std::cout << "f(const Foo&)\n";
}

int main()
{
    std::unique_ptr<Foo> p1(new Foo);  // p1 owns Foo
    if (p1) p1->bar();

    {
        //p1->bar();
        std::unique_ptr<Foo> p2(std::move(p1));  // now p2 owns Foo
        f(*p2);
        p1->bar();
        if(p1==nullptr)
        {
            std::cout<<"NULL"<<std::endl;
        }
        p1 = std::move(p2);  // ownership returns to p1
        std::unique_ptr<Foo> p3;
        p3->bar();
        std::cout << "destroying p2...\n";
    }

    if (p1) p1->bar();

    // Foo instance is destroyed when p1 goes out of scope
}

So now my question is, although p1 is guaranteed to be nullptr after move operation, it seemed still is pointing to the previous object?