How to fix menu accelerator/shortcut

Dear Sirs,
I need to fix underscored letter in menus. I use german mutation, so I need press Alt-d for Datei menu (File) and then again D for exporting to PDF.
I cannot force the program to underscore D in the menu “export to PDF”
I tried to put “&” in front of PDF, but it does not works.
I use libreoffice 4, lubuntu 13.4
Can you help me please?
thanks
x

This problem occurs on Ubuntu (with unity) as well.

To fix the problem, I did change desktop environment to gnome-shell.