PVS-Studio warning V547 for Ultimate ToolBox

BOOL CMaskData::IsValidInput(TCHAR chNewChar)
{
   ...
  if((chNewChar >= 128) && (chNewChar <= 255))
    bIsValidInput=TRUE ;
  ...
}

This suspicious code was found in Ultimate ToolBox project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'chNewChar >= 128' is always false. The value range of signed char type: [-128, 127]. UT oxmaskededit.cpp 81

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