QBS generates wrong mkspecs path for windres.exe (MinGW)

QBS generates a worng include path for qt mkspecs when calling windres from MinGW. The generates command line is:

C:/mingw/bin/windres.exe -D UNICODE -D _UNICODE -D _WINDOWS -D _USRDLL -D WIN32 -D QT_CORE_LIB -D QT_GUI_LIB -I c:/qt/4.8.5_gcc/mkspecs/D:/dl/dev/qt/485/mkspecs/win32-g++ -I c:/qt/4.8.5_gcc/include/QtCore -I c:/qt/4.8.5_gcc/include -I D:/project/project-build/qtc_Qt_4_8_5_GCC-debug/GeneratedFiles/project -I c:/qt/4.8.5_gcc/include -I c:/qt/4.8.5_gcc/include/QtGui -i D:/project/resources.rc -o D:/project/resources_res.o

the wrong part is:
-I c:/qt/4.8.5_gcc/mkspecs/D:/dl/dev/qt/485/mkspecs/win32-g++

it works if I modify the include path like:
-I c:/qt/4.8.5_gcc/mkspecs/win32-g++

The strange thing, D:/dl/dev/qt/485 is the path I compiled Qt, c:/qt/4.8.5_gcc is where I installed it to (I set the install path with configure -prefix c:\qt\4.8.5_gcc) the other Qt includes are correct, just the mkspecs path is wrong. qmake -query shows the correct mkspecs path QMAKE_MKSPECS: c:\qt\q.8.5_gcc\mkspecs