std::tr1::hash specialization for a private nested class...

[rconan]

I have a class similar to the following:

// If I place the specialization here then Outer::Nested hasn't been defined.
class Outer {
public:
    ...
private:
    class Nested {
        ...
    };
    ...
    unordered_map<Nested, ...> map;
    ...
};
// If I place the specialization here then it's after it's first instantiation. 

I'm trying to work out where I can put a specialization of std::tr1::hash for the class Nested. Everything I've tried has thrown errors.