[xmonad] XMonad.Prompt.Workspace error

[Matt Brown]

I copied the following lines from XMonad.Prompt.Workspace usage:

import XMonad.Prompt
import XMonad.Prompt.Workspace

   , ((modMask x .|. shiftMask, xK_m     ), workspacePrompt
defaultXPConfig (windows . W.shift))


but when I reload xmonad, I get this error:

Not in scope: 'W.shift'


am I missing an import or something?

thanks
-matt