Android ndk gcc problem with inherited attribute

Hi,
    I've got another problem (as in "Inheritance and friendship" post) and
I don't know if it comes from a C++ misuse or from a compiler error.

Visual Studio 2010 builds correctly but android ndk r9 gcc returns an
error.

The error refers to the line
    mInt += 1 ;
and is:
    error: 'mInt' was not declared in this scope

I think I can solve changing the line in
                 Base<T>::mInt += 1 ;
.... but why? My original code was wrong? Are there anydownsides with the
change I've applied? Or is it a good thing to do everytime?

The code is very similar to the previuous I posted:

---- MaGoTest.hpp BEGIN ----

template <class T>
class Base
{

public:
    static void Build()
         {
                 new T() ;
         }

protected:
         static int mInt ;

} ;

template<class T>
int Base<T>::mInt ;

template <class T>
class Der : public Base< T >
{

public:
    static void Build()
         {
                 mInt += 1 ;
                 Base<T>::Build() ;
         }

} ;

class A : public Der< A >
{
         template <class T> friend class ::Base ;
         template <class T> friend class ::Der ;

private:
         A() ;

} ;

---- MaGoTest.hpp END ----

---- MaGoTest.cpp BEGIN ----

#include "MaGoTest.hpp"
#include <iostream>

A::A()
{
         std::cout << "A constructor" << std::endl ;
}

---- MaGoTest.cpp END ----

---- main.cpp BEGIN ----

#include "MaGoTest.hpp"

int main( void )
{
         A::Build() ;

         return 0 ;
}

---- main.cpp END ----