Cannot use F8 for switching applications in GNOME 3.4.2.1

[Xue Fuqiao <xfq free gmail com>]

Hi list,

I'd like to use F8 (instead of Alt+Tab) for switching applications.  I
tried setting "switch applications" to F8 in Settings -> Keyboard ->
Shortcuts -> Navigation, but it didn't help; neither Alt+Tab nor F8
worked after that change.

I'm using GNOME 3.4.2.1 on Debian testing.  I've searched the web and
archives of this list, but didn't get anything that looked promising.
Can anyone point me in the right direction?  Thanks!

(English is not my native language; please excuse typing errors.)

-- 
Best regards, Xue Fuqiao.