Test program:

#include <iostream>
#include "ns3/simulator-module.h"

int main ()
{
  std::cout << (ns3::Scalar (0.9) / ns3::Scalar (1.0)).GetDouble () << "\n";
  return 0;
}

Expected output: 0.9 
Actual output (ns-3-dev changeset:   6103:12931126ea21) : -0.1