TF1 and TF2's x and y title

If I set x and y axis title by TF1 or TF2 constructor, then spaces between words in x and y title will be missing. What is my problem? Or a bug?

TF2 * f2 = new TF2("f2", "TMath::Sqrt(x/(1+y)); Signal Events; Ratio of Bkg over Sig",  0, 10, 0, 1);

ROOT version: 5.18

The title of a TF2 (TF1) is conisdered as a TFormula. This class drop the white spaces. You can do the following:

f2->SetTitle("TMath::Sqrt(x); Signal Events; Ratio of Bkg over Sig")

and the white spaces will come back.