Trouble with include headers path through prf file

I create my.prf:

    INCLUDEPATH += $$_PRO_FILE_PWD_/inc #there is my included headers is located

my.prf located at project dir $$_PRO_FILE_PWD_

And I add string to the project:

    CONFIG += my

I'm getting an error:

    error: someinc.h: No such file or directory
     #include "someinc.h"

I also try set clear path:

    INCLUDEPATH += /home/myhome/project/inc #there is my included headers is located

I get the same error.

I'm trying QMAKESPEC property (http://qt-project.org/doc/qt-4.8/qmake-advanced-usage.html#adding-new-configuration-features) . I get the same error.

load() not work too.