--AM_YFLAGS = -Wno-yacc -Wno-other -Werror=conflicts-sr -Werror=conflicts-rr
-+AM_YFLAGS = -Wnone -Werror=conflicts-sr -Werror=conflicts-rr
+-AM_YFLAGS = -Wno-yacc -Wno-other -Werror=conflicts-sr -Werror=conflicts-rr -Wcounterexamples
++AM_YFLAGS = -Wnone -Werror=conflicts-sr -Werror=conflicts-rr -Wcounterexamples