How to set environment variable in KDE desktop file

I need to set GDK_BACKEND=x11 prior to launching Eclipse, because of https://bugs.kde.org/show_bug.cgi?id=389495 . I tried the following in the .desktop file: Exec=GDK_BACKEND=x11 /home/glodt/Software/eclipse-4.7/eclipse Exec=env GDK_BACKEND=x11 /home/glodt/Software/eclipse-4.7/eclipse Exec=export GDK_BACKEND=x11; /home/glodt/Software/eclipse-4.7/eclipse but none of them yield the expected result. When I launch Eclipse from the command-line like this it works: GDK_BACKEND=x11 /home/glodt/Software/eclipse-4.7/eclipse How can I set this environment variable in the desktop file ?