I have such example of include dirs: ``` INC = -I$(WXWIN)\include -I$(PYTHONHOME)\include -I$(WXCURL)\include ``` where environmental constants are used. As we see here, backslash is not escaped. Must be: ``` INC = -I$(WXWIN)\\include -I$(PYTHONHOME)\\include -I$(WXCURL)\\include ```