RooFormulaVar with ROOTv3.10 vs v4.01

Hello,

I find that RooFormulaVar works in an old release and not in a newer one.  I don't see the problem posted here, so I'll report my findings.

I am trying to use RooFormulaVar to define my PDF. I am using RooFit that I compiled against ROOTv4.01 in Scientific Linux 3.  To start off, I have created a simple PDF:

  //---+
  // 1 |
  //---+

  // Create the Gaussian centered at 0
  RooRealVar * x = new RooRealVar("x","x",0.0,-10.0,10.0) ;
  RooRealVar * width = new RooRealVar("width","width",1.0) ;
  RooRealVar * mean = new RooRealVar("mean","mean",0.0) ;
  RooAbsPdf * gauss = new RooGaussian("gauss","gauss",*x,*mean,*width) ;

This works fine.  Now I try to use RooFormulaVar

  //---+
  // 2 |
  //---+

  // Create the Gaussian centered at 5
  RooAbsReal * mean2 = new RooFormulaVar("mean2","mean2","@0+5",RooArgList(*mean)) ;
  RooAbsPdf * gaussian2 = new RooGaussian("gauss2","gauss2",*x,*mean2,*width) ;

This crashes with:

*ERROR 30 :
Bad numerical expression : "mean"
RooFormula::RooFormula(mean2): compile error
RooFormula::eval(mean2): Formula doesn't compile: mean*2
RooFormula::eval(mean2): Formula doesn't compile: mean*2

After checking the syntax many times, I tried an older RooFit version that I compiled against ROOT v3.10 on RedHat 7.2, and it worked!

One thing I do want to know is whether this is a RooFit problem (RooFormulaVar) or a ROOT problem (TFormula).

regards,
Tae Min