Interfacing to C++: Cannot access value from namespace

[Andrew Edwards via Digitalmars-d-learn]

I'm running into the following issue when attempting to interface 
with C++:

// C++
========
namespace MySpace
{
    MyType& GetData();
}
struct MyType
{
    // ...
    float continuallyUpdatedValue;
    // ...
};

// call site
MySpace::GetData().continuallyUpdatedValue;

// D
========
extern (C++, MySpace) MyType* GetData();

struct MyType
{
    float continuallyChangingValue; // [1]
}

// call site
MySpace.GetData().continuallyUpdatedValue; // <--- This is not 
being updated by C++

[1] I did not declare any of the other member variables from the 
struct, don't know if this is a source of the problem.