Possible bug in QDialog

[GrahamL]

Hello
I would be grateful if some one could confirm the following behaviour in Qt5
Create a dialog
add some widgets
for these widgets add a Whats This string.
When the dialog is displayed and the '?' is pressed I get the whats this cursor but not what this is displayed.

When compiled for Qt4.8.2 the dialog behaves as expected.

Is this a bug or have things changed in Qt5?

Thanks