sfinae check for static member using decltype

I've written the below code to try to detect if a type has a static member variable. Unfortunately, it's always returning that the variable does not exist.

Could someone tell me where I'm going wrong? I'm using g++ 4.7.1.

#include <iostream>
#include <utility>
#include <type_traits>

using namespace std;

template <class T>                                                  
class has_is_baz                                                          
{                                                                   
    template<class U, 
             typename std::enable_if<std::is_same<bool, decltype(U::is_baz)>::value>::type...>                    
        static std::true_type check(int);                           
    template <class>                                                
        static std::false_type check(...);                          
public:                                                             
    static constexpr bool value = decltype(check<T>(0))::value;     
};

struct foo { };

struct bar 
{ 
    static constexpr bool is_baz = true;
};

int main()
{
    cout << has_is_baz<foo>::value << '\n';
    cout << has_is_baz<bar>::value << '\n';
}