TMS320F28069M: Resolving static class variables by linker

Why am I unable to use a static class variable in my code when using standard 28069_RAM_lnk.cmd?

Error given (at link time): undefined symbol ADC:nAdcClassVariable.

I can use a global to accomplish the same behavior, but I'd like to use a class variable.

//------------------------------------------------------------------------------
// ADC class
//------------------------------------------------------------------------------
class ADC
{
public:

    static int nAdcClassVariable;
    static void InitModule( void );

};

//------------------------------------------------------------------------------
//Initialization of ADC Module
//------------------------------------------------------------------------------
void ADC::InitModule()
{
    
    nAdcClassVariable = 4;  //link error when trying to use/assign class variable

    return;
}