Can't handle "Helvetica Neue" weight correctly

Simply create a QWebView and try to print some sentences with font-family:'Helvetica Neue' and use different font-weight. (or go to this webpage : http://dev.l-c-n.com/CSS2/font-weight/font-weight_100_900-HelveNeue.html)

In Qt 4.8.4, we can see a difference between 100 and 300, but not in Qt 5.1.1.
(The default is 300, but it looks like the 100)

(on the screenshot, you have Qt4 on left and Qt5 on right)

UPDATE:
Even setting the font weight with different values has no effect.Further fonts sub-styles that have the style "condensed" also does not work.
seem to work.
This can be easily reproduce using Qt font sampler example (QTDIR/qtbase/example/widgets/painting) It seems it is is not only limited to Helvetica font but other too.