C++ – Cannot open include file: ‘QWebView’: No such file or directory

I have followed the instructions on the following page:

http://qt-project.org/wiki/Open_Web_Page_in_QWebView

I added QT += webkit in my pro file and ran qmake, then clean all and compile again. I still get:

error: C1083: Cannot open include file: 'QWebView': No such file or
directory

when I add #include <QWebView> in header and cpp file. Any ideas?