Shortcuts with Ctrl-modifier not working

With Qt 5.7 any in-application shortcut with ctrl-modifier is not working. Shortcuts with the alt-modifier (e.g. the menu) are working.

Steps to reproduce:
1. Start a Wayland compositor (e.g. Weston or KWin)
2. Open a Qt application which uses ctrl-modifier shortcuts, e.g. KWrite
3. try to trigger a shortcut, e.g. ctrl+o for file open

Actual Result:
Nothing happens

Expected Result:
Shortcut triggered

With Qt 5.6 the shortcuts are working. So this seems to be a regression in Qt 5.7.