#18 xxkb application lists have no effect

[Max]

I use CapsLock as group switch key (USB keyboard):

KeyPress event, serial 32, synthetic NO, window 0x1600001,
root 0x55, subw 0x0, time 5552881, (-183,38), root:(158,417),
state 0x10, keycode 66 (keysym 0xfe08, ISO_Next_Group), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False

Among other things, my .xxkbrc contains this:
XXkb.app_list.wm_class_class.ignore: urxvt* URxvt*
XXkb.app_list.wm_class_class.alt_group1: urxvt* URxvt*

But I'm still able to switch keyboard group in terminal. xprop shows WM_CLASS(STRING) = "urxvt", "URxvt"
Same result with both xxkb-1.10 and xxkb-1.11. I've tried to add some 'warnx' statements in xxkb code to track why it fails, but failed to understand what it does.

Can you please help me? I'm willing to help in debugging (can apply patches and recompile).