Is there any limit of how many workspaces compiz can goto using "Switch to viewport"? If so, can this limit be changed or worked around?

I have configured 12 viewports, (4 * 3 under desktop size) on ubuntu 14.04. I've mapped all 12 viewports to key commands in compiz under
"Viewport switcher" -> "Goto specific viewport"
mapping the switch to control, alt and another letter on the keyboard as such:

• control+alt+q: "Switch to viewport 1"


• control+alt+w: "Switch to viewport 2"


• control+alt+e: "Switch to viewport 3"


• control+alt+r: "Switch to viewport 4"


• control+alt+a: "Switch to viewport 5"


• control+alt+s: "Switch to viewport 6"


• control+alt+d: "Switch to viewport 7"


• control+alt+f: "Switch to viewport 8"


• control+alt+z: "Switch to viewport 9"


• control+alt+x: "Switch to viewport 10"


• control+alt+c: "Switch to viewport 11"


• control+alt+v: "Switch to viewport 12"

The first 10 works, "Switch to viewport 11" and "Switch to viewport 12" does not work.

Using the workspace switcher, however, I can click on the last 2 workspaces and go to them that way. So it seemes to be supported.

I can also move windows to all 12 workspaces using a mapping I've made under
Window manager -> Put -> Bindings -> Put on arbirtrary viewport -> "Put on viewport X" using 12 similar key commands (shift+alt instead of control+alt)