QX11EmbedWidget looses focus after undock->dock when embedded in QDockWidget

The QMainWindow contains 2 QDockWidgets and both of them contain QX11EmbedContainer. Both QX11EmbedContainer run same application, which contains QMainWindow with a QDockWidget, which contains QTextEdit.

Now, if you undock any of the dock widgets and then dock it back the undocked-docked widget is not able to get the focus anymore. The mouse pointer changes to 'I' when you hover on top of the text edit, but you are not able to gain the focus by clicking it. You can get the focus back if you move any other dock widget in the main window (no need to undock them).

Find attached an example to reproduce the problem. First compile "widget", then "container" and run the "container".