Ubuntu – xorg.conf XkbOption ignored for terminate:ctrl_alt_bksp to restart X

I want Ctrl+Alt+Bksp to restart X, so I created an xorg.conf rule:

/usr/share/X11/xorg.conf.d/53-zap.conf:

Section "ServerFlags"
    Option "DontZap" "false"
EndSection

Section "InputClass"
    Identifier      "Keyboard Defaults"
    MatchIsKeyboard "yes"
    Option          "XkbOptions" "terminate:ctrl_alt_bksp"
EndSection

And checking /var/log/Xorg.0.log:

[  1023.598] (II) XINPUT: Adding extended input device "Asus WMI hotkeys" (type: KEYBOARD, id 11)
[  1023.598] (**) Option "xkb_rules" "evdev"
[  1023.598] (**) Option "xkb_model" "pc105"
[  1023.598] (**) Option "xkb_layout" "us"
[  1023.598] (**) Option "xkb_options" "terminate:ctrl_alt_bksp"
[  1023.598] (II) config/udev: Adding input device AT Translated Set 2 keyboard (/dev/input/event3)
[  1023.598] (**) AT Translated Set 2 keyboard: Applying InputClass "evdev keyboard catchall"
[  1023.598] (**) AT Translated Set 2 keyboard: Applying InputClass "Keyboard Defaults"
[  1023.598] (II) Using input driver 'evdev' for 'AT Translated Set 2 keyboard'
[  1023.598] (**) AT Translated Set 2 keyboard: always reports core events
[  1023.598] (**) evdev: AT Translated Set 2 keyboard: Device: "/dev/input/event3"
[  1023.598] (--) evdev: AT Translated Set 2 keyboard: Vendor 0x1 Product 0x1
[  1023.598] (--) evdev: AT Translated Set 2 keyboard: Found keys
[  1023.598] (II) evdev: AT Translated Set 2 keyboard: Configuring as keyboard
[  1023.598] (**) Option "config_info" "udev:/sys/devices/platform/i8042/serio0/input/input3/event3"
[  1023.598] (II) XINPUT: Adding extended input device "AT Translated Set 2 keyboard" (type: KEYBOARD, id
 12)
[  1023.598] (**) Option "xkb_rules" "evdev"
[  1023.598] (**) Option "xkb_model" "pc105"
[  1023.598] (**) Option "xkb_layout" "us"
[  1023.598] (**) Option "xkb_options" "terminate:ctrl_alt_bksp"

The last line shows that it sees the directive.

And yet, when I open a terminal and type setxkbmap -print -verbose 10

Setting verbose level to 10
locale is C
Trying to load rules file ./rules/evdev...
Trying to load rules file /usr/share/X11/xkb/rules/evdev...
Success.
Applied rules from evdev:
rules:      evdev
model:      pc105
layout:     us
Trying to build keymap using the following components:
keycodes:   evdev+aliases(qwerty)
types:      complete
compat:     complete
symbols:    pc+us+inet(evdev)
geometry:   pc(pc105)
xkb_keymap {
    xkb_keycodes  { include "evdev+aliases(qwerty)" };
    xkb_types     { include "complete"  };
    xkb_compat    { include "complete"  };
    xkb_symbols   { include "pc+us+inet(evdev)" };
    xkb_geometry  { include "pc(pc105)" };
};

I can force the option, setxkbmap -option terminate:ctrl_alt_bksp,
giving me:

...
model:      pc105
layout:     us
options:    terminate:ctrl_alt_bksp
Trying to build keymap using the following components:
...

And I test it and it restarts X correctly.

I don't understand. I had this working last week, but now it doesn't load the XkbOption from the xorg.conf file. Is there another layer that sets XKB settings that I don't know about?

I'm using Ubuntu 13.10, but with xmonad. I load some gnome utilities (gnome-panel, gnome-screensaver, gnome-keyring-demon), but not gnome-settings-daemon.