Using static const + const as array bound

Question

I'm doing something like this

Class.hpp:

 class Class {

 private:
     static const unsigned int arraySize;
     int ar[arraySize+2];
 };

Class.cpp:

#include <Class.hpp>
const unsigned int arraySize = 384;

The compiler (q++, a c++ compiler for the QNX OS based on g++) gives me error: array bound is not an integer constant while compiling a unit including Class.hpp (not while compiling Class.cpp).

Why isn't that working? I know that a static const member can be used as an array bound, guaranteed by the C++ standard (see this anwser). But why doesn't the compiler see the result of static const + const as a constant?