I wanted to use vc++ compiler from within Qt Creator. Therefore I set QMAKESPEC environment variable in Projects/Build Settings/Debug to c:\qt\4.5.2-vc\mkspecs\win32-msvc2008 where I have qt compiled with vc++ compiler.
But when building a project I get this error
Starting: C:/qt/4.5.2-vc/bin/qmake.exe D:/projects/qt-test/formextractor.pro -spec Z:/qt-src/mkspecs/win32-g++ -r
Failure to read QMAKESPEC conf file z:/qt-src/mkspecs/win32-g++\qmake.conf.

Why qmake doesn't read QMAKESPEC variable and instead keeps using z:/qt-src/mkspecs/win32-g++\qmake.conf as a value of spec option?
How can I fix this?