template & friend problem

[Regel]

#include <iostream>
using namespace std;

template<class T>
class Stack
{
private:
	T* arr;
	int size;
public:
	friend ostream& operator<<(ostream& os, const Stack& x);
};

template<class T>
ostream& operator<<(ostream& os, const Stack<T>& x)
{
	for(int i=0; i < x.size; i++)
		os << x.arr[i] << endl;
	return os;
}

int main()
{
	Stack<int> x;
	cout << x << endl;
}

it gives me a linker error:
unresolved external symbol "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class Stack<int> const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@std@@AAV01@ABV?$Stack@H@@@Z) referenced in function _main

[laserlight]

I usually refer to this FAQ whenever I forget the incantation needed to work with template friends:
Why do I get linker errors when I use template friends?

[Regel]

Thanks!