qt4support/install-helper.pri: target_headers.path should not use $$[QT_INSTALL_PREFIX]/include, but should rather use $$[QT_INSTALL_HEADERS]. This is especially critical when the qt headers were NOT installed in $${QT_INSTALL_PREFIX]/include, like on RedHat systems.

I got around it by moving the headers after the install phase inside my rpm spec file, but shouldn't need to be done - thought you'd want to know so you can continue to support Qt4 correctly.