Keyboard shortcuts not triggering

The attached C++ program creates a derived QMainWindow with a single action with the shortcut set to the "d" key. The action is added to both the menu and the main window. Using a custom QMenuBar with an key event handler and another handler on the main window, it shows that the main window is receiving the "d" key presses, but the action is not triggered. When the menu is opened, it also receives the "d" key presses, but the action is still not triggered. Using the keyboard to trigger the menu button does trigger the action, as does using the mouse.