How do I make C++ friend template specializations work?

I have a class that overloads the bit shift operator like the following:

    template<typename DataType>
    friend Packet& operator << (Packet& pkt, const DataType& data)
    {
          std::cout << "this compiles" << std::endl;
    }

but when I try to make a specialization of it like this :

    template<typename DataType>
    friend Packet& operator << (Packet& pkt, const DataType& data)
    {
          std::cout << "this doesn't compile" << std::endl;
    }

    template<>
    friend Packet& operator<<<std::string> (Packet& pkt, const std::string& data)
    {
          std::cout << "this doesn't compile" << std::endl;
    }

it throws a compile time error:

Error   C2116   'operator <<': function parameter lists do not match between declarations 

what I'm I doing wrong here ?