Log Scale of histogram - does not show my signal

[Leonitd]

Dear ROOT experts,
I have struggled with log scale of the stack histograms (2 backgrounds are stacked and 1 signal is plotted on top of them).
I defined my stack histogram as:

      histostack_log->Add(histo3); // Background A
      histostack_log->Add(histo2); // Background B
      histostack_log->Draw("");
      histo1->Draw("same"); // Signal
      cv1_2->Update(); // address my pad
      cv1_2->SetLogy(); // change pad to log scale

The problem is that it automatically changes the y-range so the signal is invisible. I tried to force the range. I was unsuccessful.
In the first case (I have overflow of backgrounds), it draws the y-range correctly:

But in the second case (I just extended x-range to 1000 - and tried to interchange QCD and EWK):

The signal does not appear.

Thank you for your help.

[Wile_E_Coyote]

Try:
histostack_log->SetMinimum(1.0);

[Leonitd]

It works. Thank you