[xmonad] XMonad 0.10 only matches on last className?

[Joseph Garvin]

If I run xprop on my emacs I see this:

WM_CLASS(STRING) = "emacs", "Emacs23"

If I setup a keybinding to runOrRaise looking for "emacs", it always
starts a new instance:

    , ((modMask,  xK_w), runOrRaiseNext editor (className =? "emacs"))

If I change it to match on Emacs23, then I get the expected runOrRaise behavior:

    , ((modMask,  xK_w), runOrRaiseNext editor (className =? "Emacs23"))

Is this a bug, or is there a different syntax I'm supposed to use for
when I want to match on any of the WM_CLASS's that the window has
specified?